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Operations and Properties of Complex Numbers Quiz

#1

What is the modulus of the complex number 3 + 4i?

5
Explanation

The modulus (or magnitude) of a complex number a + bi is given by sqrt(a^2 + b^2). In this case, sqrt(3^2 + 4^2) = 5.

#2

What is the conjugate of the complex number 2 - 3i?

2 + 3i
Explanation

The conjugate of a complex number a - bi is a + bi. In this case, the conjugate is 2 + 3i.

#3

What is the modulus of the complex number (-3 + 4i)?

5
Explanation

The modulus (absolute value) of a complex number a + bi is given by sqrt(a^2 + b^2). In this case, sqrt((-3)^2 + 4^2) = 5.

#4

What is the modulus of the complex number (-5 - 12i)?

13
Explanation

The modulus (absolute value) of a complex number a + bi is given by sqrt(a^2 + b^2). In this case, sqrt((-5)^2 + (-12)^2) = 13.

#5

What is the modulus of the complex number (1 - i)?

√2
Explanation

The modulus (absolute value) of a complex number a + bi is given by sqrt(a^2 + b^2). In this case, sqrt(1^2 + (-1)^2) = √2.

#6

Which of the following is true about the product of two complex conjugates?

Always a real number
Explanation

The product of two complex conjugates (a + bi)(a - bi) is always a real number. It simplifies to a^2 + b^2.

#7

What is the square of the complex number 1 + i?

1 - i
Explanation

To square a complex number a + bi, multiply it by itself. In this case, (1 + i)^2 = 1 - i.

#8

What is the argument (angle) of the complex number -1 + √3i in radians?

π/3
Explanation

The argument (angle) of a complex number a + bi is arctan(b/a). In this case, arctan(√3/(-1)) = π/3.

#9

Which of the following is NOT a property of complex conjugates?

The product of two complex conjugates is always a complex number.
Explanation

The product of two complex conjugates is always a real number, not necessarily a complex number.

#10

What is the product of the complex numbers (2 + i) and (3 - 2i)?

3 + 7i
Explanation

Multiply the complex numbers using the distributive property. The product of (2 + i) and (3 - 2i) is 3 + 7i.

#11

If z = 2 + 3i and w = 4 - 2i, what is the product zw?

14 + 4i
Explanation

Multiply the complex numbers using the distributive property. The product of (2 + 3i) and (4 - 2i) is 14 + 4i.

#12

If z = 3 - 2i and w = -1 + 4i, what is the quotient z/w?

0.5 - 0.5i
Explanation

Divide the complex numbers using the formula (a + bi)/(c + di) = (ac + bd)/(c^2 + d^2) + (bc - ad)/(c^2 + d^2)i.

#13

What is the cube of the complex number 1 - i?

1 + 3i
Explanation

To find the cube of a complex number a + bi, multiply it by itself twice. In this case, (1 - i)^3 = 1 + 3i.

#14

If |z| = 5 and |w| = 3, what is |z - w|?

4
Explanation

The modulus (absolute value) of the difference of two complex numbers |z - w| is the same as the difference of their moduli |z| - |w|. In this case, |5 - 3| = 4.

#15

If z = 2 + 3i and w = 1 - 2i, what is the difference z - w?

3 + i
Explanation

Subtract the complex numbers by subtracting their real and imaginary parts separately. The difference of (2 + 3i) and (1 - 2i) is 3 + i.

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