Practice
Complex Numbers Practice
Fifty original questions on negative roots, powers of i, complex anatomy, arithmetic, conjugates, division, equality, and error analysis.
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Question 1
Explanation
Write \(\sqrt{-12}=i\sqrt{12}\), then extract the largest perfect-square factor. The simplified result is \(2i\sqrt3\).
- Method
Factor out square root of negative one as i, then simplify the remaining positive radical.
- Verified result
Write \(\sqrt{-12}=i\sqrt{12}\), then extract the largest perfect-square factor. The simplified result is \(2i\sqrt3\).
Question 2
Explanation
Write \(\sqrt{-27}=i\sqrt{27}\), then extract the largest perfect-square factor. The simplified result is \(3i\sqrt3\).
- Method
Factor out square root of negative one as i, then simplify the remaining positive radical.
- Verified result
Write \(\sqrt{-27}=i\sqrt{27}\), then extract the largest perfect-square factor. The simplified result is \(3i\sqrt3\).
Question 3
Explanation
Write \(\sqrt{-32}=i\sqrt{32}\), then extract the largest perfect-square factor. The simplified result is \(4i\sqrt2\).
- Method
Factor out square root of negative one as i, then simplify the remaining positive radical.
- Verified result
Write \(\sqrt{-32}=i\sqrt{32}\), then extract the largest perfect-square factor. The simplified result is \(4i\sqrt2\).
Question 4
Explanation
Write \(\sqrt{-75}=i\sqrt{75}\), then extract the largest perfect-square factor. The simplified result is \(5i\sqrt3\).
- Method
Factor out square root of negative one as i, then simplify the remaining positive radical.
- Verified result
Write \(\sqrt{-75}=i\sqrt{75}\), then extract the largest perfect-square factor. The simplified result is \(5i\sqrt3\).
Question 5
Explanation
Write \(\sqrt{-98}=i\sqrt{98}\), then extract the largest perfect-square factor. The simplified result is \(7i\sqrt2\).
- Method
Factor out square root of negative one as i, then simplify the remaining positive radical.
- Verified result
Write \(\sqrt{-98}=i\sqrt{98}\), then extract the largest perfect-square factor. The simplified result is \(7i\sqrt2\).
Question 6
Explanation
The powers of \(i\) repeat every four. Since \(17\) leaves remainder \(1\) modulo \(4\), \(i^{17}=i\).
- Method
Reduce the exponent modulo 4 and use the cycle 1, i, -1, -i.
- Verified result
The powers of \(i\) repeat every four. Since \(17\) leaves remainder \(1\) modulo \(4\), \(i^{17}=i\).
Question 7
Explanation
The powers of \(i\) repeat every four. Since \(26\) leaves remainder \(2\) modulo \(4\), \(i^{26}=-1\).
- Method
Reduce the exponent modulo 4 and use the cycle 1, i, -1, -i.
- Verified result
The powers of \(i\) repeat every four. Since \(26\) leaves remainder \(2\) modulo \(4\), \(i^{26}=-1\).
Question 8
Explanation
The powers of \(i\) repeat every four. Since \(35\) leaves remainder \(3\) modulo \(4\), \(i^{35}=-i\).
- Method
Reduce the exponent modulo 4 and use the cycle 1, i, -1, -i.
- Verified result
The powers of \(i\) repeat every four. Since \(35\) leaves remainder \(3\) modulo \(4\), \(i^{35}=-i\).
Question 9
Explanation
The powers of \(i\) repeat every four. Since \(44\) leaves remainder \(0\) modulo \(4\), \(i^{44}=1\).
- Method
Reduce the exponent modulo 4 and use the cycle 1, i, -1, -i.
- Verified result
The powers of \(i\) repeat every four. Since \(44\) leaves remainder \(0\) modulo \(4\), \(i^{44}=1\).
Question 10
Explanation
The powers of \(i\) repeat every four. Since \(59\) leaves remainder \(3\) modulo \(4\), \(i^{59}=-i\).
- Method
Reduce the exponent modulo 4 and use the cycle 1, i, -1, -i.
- Verified result
The powers of \(i\) repeat every four. Since \(59\) leaves remainder \(3\) modulo \(4\), \(i^{59}=-i\).
Question 11
Explanation
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested real part is \(7\).
- Method
Match the expression to a+bi and distinguish b from the complete term bi.
- Verified result
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested real part is \(7\).
Question 12
Explanation
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary coefficient is \(9\).
- Method
Match the expression to a+bi and distinguish b from the complete term bi.
- Verified result
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary coefficient is \(9\).
Question 13
Explanation
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary coefficient is \(-1\).
- Method
Match the expression to a+bi and distinguish b from the complete term bi.
- Verified result
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary coefficient is \(-1\).
Question 14
Explanation
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary term is \(-5i\).
- Method
Match the expression to a+bi and distinguish b from the complete term bi.
- Verified result
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested imaginary term is \(-5i\).
Question 15
Explanation
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested real part is \(11\).
- Method
Match the expression to a+bi and distinguish b from the complete term bi.
- Verified result
In standard form \(a+bi\), the real part is \(a\), the imaginary coefficient is \(b\), and the imaginary term is \(bi\). Therefore the requested real part is \(11\).
Question 16
Explanation
Add real parts and imaginary coefficients separately: \(3+(5)=8\) and \(4+(-2)=2\). The result is \(8+2i\).
- Method
Line up real parts with real parts and coefficients of i with coefficients of i.
- Verified result
Add real parts and imaginary coefficients separately: \(3+(5)=8\) and \(4+(-2)=2\). The result is \(8+2i\).
Question 17
Explanation
Add real parts and imaginary coefficients separately: \(-6+(2)=-4\) and \(3+(7)=10\). The result is \(-4+10i\).
- Method
Line up real parts with real parts and coefficients of i with coefficients of i.
- Verified result
Add real parts and imaginary coefficients separately: \(-6+(2)=-4\) and \(3+(7)=10\). The result is \(-4+10i\).
Question 18
Explanation
Add real parts and imaginary coefficients separately: \(8+(-3)=5\) and \(-5+(-4)=-9\). The result is \(5-9i\).
- Method
Line up real parts with real parts and coefficients of i with coefficients of i.
- Verified result
Add real parts and imaginary coefficients separately: \(8+(-3)=5\) and \(-5+(-4)=-9\). The result is \(5-9i\).
Question 19
Explanation
Add real parts and imaginary coefficients separately: \(1+(7)=8\) and \(9+(1)=10\). The result is \(8+10i\).
- Method
Line up real parts with real parts and coefficients of i with coefficients of i.
- Verified result
Add real parts and imaginary coefficients separately: \(1+(7)=8\) and \(9+(1)=10\). The result is \(8+10i\).
Question 20
Explanation
Add real parts and imaginary coefficients separately: \(-4+(-5)=-9\) and \(-6+(8)=2\). The result is \(-9+2i\).
- Method
Line up real parts with real parts and coefficients of i with coefficients of i.
- Verified result
Add real parts and imaginary coefficients separately: \(-4+(-5)=-9\) and \(-6+(8)=2\). The result is \(-9+2i\).
Question 21
Explanation
Distribute subtraction across both parts: real part \(7-(3)=4\), imaginary coefficient \(2-(5)=-3\). Thus the result is \(4-3i\).
- Method
Place parentheses around the subtracted complex number before combining like parts.
- Verified result
Distribute subtraction across both parts: real part \(7-(3)=4\), imaginary coefficient \(2-(5)=-3\). Thus the result is \(4-3i\).
Question 22
Explanation
Distribute subtraction across both parts: real part \(-1-(4)=-5\), imaginary coefficient \(6-(-2)=8\). Thus the result is \(-5+8i\).
- Method
Place parentheses around the subtracted complex number before combining like parts.
- Verified result
Distribute subtraction across both parts: real part \(-1-(4)=-5\), imaginary coefficient \(6-(-2)=8\). Thus the result is \(-5+8i\).
Question 23
Explanation
Distribute subtraction across both parts: real part \(9-(-2)=11\), imaginary coefficient \(-3-(7)=-10\). Thus the result is \(11-10i\).
- Method
Place parentheses around the subtracted complex number before combining like parts.
- Verified result
Distribute subtraction across both parts: real part \(9-(-2)=11\), imaginary coefficient \(-3-(7)=-10\). Thus the result is \(11-10i\).
Question 24
Explanation
Distribute subtraction across both parts: real part \(5-(6)=-1\), imaginary coefficient \(8-(1)=7\). Thus the result is \(-1+7i\).
- Method
Place parentheses around the subtracted complex number before combining like parts.
- Verified result
Distribute subtraction across both parts: real part \(5-(6)=-1\), imaginary coefficient \(8-(1)=7\). Thus the result is \(-1+7i\).
Question 25
Explanation
Distribute subtraction across both parts: real part \(-4-(-7)=3\), imaginary coefficient \(-5-(-2)=-3\). Thus the result is \(3-3i\).
- Method
Place parentheses around the subtracted complex number before combining like parts.
- Verified result
Distribute subtraction across both parts: real part \(-4-(-7)=3\), imaginary coefficient \(-5-(-2)=-3\). Thus the result is \(3-3i\).
Question 26
Explanation
FOIL and replace \(i^2\) by \(-1\). The real part is \(2(4)-3(-1)=11\), and the imaginary coefficient is \(2(-1)+3(4)=10\).
- Method
Use (a+bi)(c+di)=(ac-bd)+(ad+bc)i and verify the sign from i squared.
- Verified result
FOIL and replace \(i^2\) by \(-1\). The real part is \(2(4)-3(-1)=11\), and the imaginary coefficient is \(2(-1)+3(4)=10\).
Question 27
Explanation
FOIL and replace \(i^2\) by \(-1\). The real part is \(5(1)--2(3)=11\), and the imaginary coefficient is \(5(3)+-2(1)=13\).
- Method
Use (a+bi)(c+di)=(ac-bd)+(ad+bc)i and verify the sign from i squared.
- Verified result
FOIL and replace \(i^2\) by \(-1\). The real part is \(5(1)--2(3)=11\), and the imaginary coefficient is \(5(3)+-2(1)=13\).
Question 28
Explanation
FOIL and replace \(i^2\) by \(-1\). The real part is \(-3(2)-4(2)=-14\), and the imaginary coefficient is \(-3(2)+4(2)=2\).
- Method
Use (a+bi)(c+di)=(ac-bd)+(ad+bc)i and verify the sign from i squared.
- Verified result
FOIL and replace \(i^2\) by \(-1\). The real part is \(-3(2)-4(2)=-14\), and the imaginary coefficient is \(-3(2)+4(2)=2\).
Question 29
Explanation
FOIL and replace \(i^2\) by \(-1\). The real part is \(1(-2)--5(3)=13\), and the imaginary coefficient is \(1(3)+-5(-2)=13\).
- Method
Use (a+bi)(c+di)=(ac-bd)+(ad+bc)i and verify the sign from i squared.
- Verified result
FOIL and replace \(i^2\) by \(-1\). The real part is \(1(-2)--5(3)=13\), and the imaginary coefficient is \(1(3)+-5(-2)=13\).
Question 30
Explanation
FOIL and replace \(i^2\) by \(-1\). The real part is \(6(3)-1(-4)=22\), and the imaginary coefficient is \(6(-4)+1(3)=-21\).
- Method
Use (a+bi)(c+di)=(ac-bd)+(ad+bc)i and verify the sign from i squared.
- Verified result
FOIL and replace \(i^2\) by \(-1\). The real part is \(6(3)-1(-4)=22\), and the imaginary coefficient is \(6(-4)+1(3)=-21\).
Question 31
Explanation
The conjugate is \(3-4i\). Their product is \(3^2+(4)^2=25\), a real number.
- Method
A complex number times its conjugate equals the sum of the squares of its two coefficients.
- Verified result
The conjugate is \(3-4i\). Their product is \(3^2+(4)^2=25\), a real number.
Question 32
Explanation
The conjugate is \(-2-5i\). Their product is \(-2^2+(5)^2=29\), a real number.
- Method
A complex number times its conjugate equals the sum of the squares of its two coefficients.
- Verified result
The conjugate is \(-2-5i\). Their product is \(-2^2+(5)^2=29\), a real number.
Question 33
Explanation
The conjugate is \(7+i\). Their product is \(7^2+(-1)^2=50\), a real number.
- Method
A complex number times its conjugate equals the sum of the squares of its two coefficients.
- Verified result
The conjugate is \(7+i\). Their product is \(7^2+(-1)^2=50\), a real number.
Question 34
Explanation
The conjugate is \(1-6i\). Their product is \(1^2+(6)^2=37\), a real number.
- Method
A complex number times its conjugate equals the sum of the squares of its two coefficients.
- Verified result
The conjugate is \(1-6i\). Their product is \(1^2+(6)^2=37\), a real number.
Question 35
Explanation
The conjugate is \(-4+3i\). Their product is \(-4^2+(-3)^2=25\), a real number.
- Method
A complex number times its conjugate equals the sum of the squares of its two coefficients.
- Verified result
The conjugate is \(-4+3i\). Their product is \(-4^2+(-3)^2=25\), a real number.
Question 36
Explanation
Multiply numerator and denominator by the conjugate of \(2-i\). The denominator becomes \(5\), and simplifying the numerator gives \(\frac95+\frac75i\).
- Method
Use the denominator's conjugate so its product becomes a real sum of squares.
- Verified result
Multiply numerator and denominator by the conjugate of \(2-i\). The denominator becomes \(5\), and simplifying the numerator gives \(\frac95+\frac75i\).
Question 37
Explanation
Multiply numerator and denominator by the conjugate of \(1-2i\). The denominator becomes \(5\), and simplifying the numerator gives \(-1+2i\).
- Method
Use the denominator's conjugate so its product becomes a real sum of squares.
- Verified result
Multiply numerator and denominator by the conjugate of \(1-2i\). The denominator becomes \(5\), and simplifying the numerator gives \(-1+2i\).
Question 38
Explanation
Multiply numerator and denominator by the conjugate of \(3+i\). The denominator becomes \(10\), and simplifying the numerator gives \(2-i\).
- Method
Use the denominator's conjugate so its product becomes a real sum of squares.
- Verified result
Multiply numerator and denominator by the conjugate of \(3+i\). The denominator becomes \(10\), and simplifying the numerator gives \(2-i\).
Question 39
Explanation
Multiply numerator and denominator by the conjugate of \(1+i\). The denominator becomes \(2\), and simplifying the numerator gives \(3-i\).
- Method
Use the denominator's conjugate so its product becomes a real sum of squares.
- Verified result
Multiply numerator and denominator by the conjugate of \(1+i\). The denominator becomes \(2\), and simplifying the numerator gives \(3-i\).
Question 40
Explanation
Multiply numerator and denominator by the conjugate of \(2+i\). The denominator becomes \(5\), and simplifying the numerator gives \(\frac75+\frac95i\).
- Method
Use the denominator's conjugate so its product becomes a real sum of squares.
- Verified result
Multiply numerator and denominator by the conjugate of \(2+i\). The denominator becomes \(5\), and simplifying the numerator gives \(\frac75+\frac95i\).
Question 41
Explanation
Equal complex numbers have matching parts. From \(a+2=8\), \(a=6\). From \(3b-1=11\), \(b=4\). Therefore \(a+b=10\).
- Method
Write one equation for real parts and another for imaginary coefficients.
- Verified result
Equal complex numbers have matching parts. From \(a+2=8\), \(a=6\). From \(3b-1=11\), \(b=4\). Therefore \(a+b=10\).
Question 42
Explanation
Equal complex numbers have matching parts. From \(a-4=3\), \(a=7\). From \(2b+5=-1\), \(b=-3\). Therefore \(a+b=4\).
- Method
Write one equation for real parts and another for imaginary coefficients.
- Verified result
Equal complex numbers have matching parts. From \(a-4=3\), \(a=7\). From \(2b+5=-1\), \(b=-3\). Therefore \(a+b=4\).
Question 43
Explanation
Equal complex numbers have matching parts. From \(a+7=-2\), \(a=-9\). From \(-1b+4=9\), \(b=-5\). Therefore \(a+b=-14\).
- Method
Write one equation for real parts and another for imaginary coefficients.
- Verified result
Equal complex numbers have matching parts. From \(a+7=-2\), \(a=-9\). From \(-1b+4=9\), \(b=-5\). Therefore \(a+b=-14\).
Question 44
Explanation
Equal complex numbers have matching parts. From \(a-3=5\), \(a=8\). From \(4b-2=10\), \(b=3\). Therefore \(a+b=11\).
- Method
Write one equation for real parts and another for imaginary coefficients.
- Verified result
Equal complex numbers have matching parts. From \(a-3=5\), \(a=8\). From \(4b-2=10\), \(b=3\). Therefore \(a+b=11\).
Question 45
Explanation
Equal complex numbers have matching parts. From \(a+1=6\), \(a=5\). From \(-2b+3=-7\), \(b=5\). Therefore \(a+b=10\).
- Method
Write one equation for real parts and another for imaginary coefficients.
- Verified result
Equal complex numbers have matching parts. From \(a+1=6\), \(a=5\). From \(-2b+3=-7\), \(b=5\). Therefore \(a+b=10\).
Question 46
Explanation
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
- Method
Reduce the work to a+bi form and check every occurrence of i squared or a conjugate sign.
- Verified result
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
Question 47
Explanation
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
- Method
Reduce the work to a+bi form and check every occurrence of i squared or a conjugate sign.
- Verified result
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
Question 48
Explanation
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
- Method
Reduce the work to a+bi form and check every occurrence of i squared or a conjugate sign.
- Verified result
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
Question 49
Explanation
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
- Method
Reduce the work to a+bi form and check every occurrence of i squared or a conjugate sign.
- Verified result
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
Question 50
Explanation
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
- Method
Reduce the work to a+bi form and check every occurrence of i squared or a conjugate sign.
- Verified result
Complex arithmetic follows ordinary distribution and like-term rules together with the defining identity \(i^2=-1\). The stated correction preserves those rules.
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