Given a complex number [tex]z = -3 + 2i[/tex], what is [tex]|z|[/tex]?

A. [tex]-\sqrt{5}[/tex]
B. [tex]-\sqrt{13}[/tex]
C. [tex]\sqrt{13}[/tex]
D. [tex]\sqrt{5}[/tex]



Answer :

To find the magnitude (or modulus) of a complex number [tex]\( z = a + bi \)[/tex], we use the formula:

[tex]\[ |z| = \sqrt{a^2 + b^2} \][/tex]

Given the complex number [tex]\( z = -3 + 2i \)[/tex]:

1. Identify the real part [tex]\( a \)[/tex] and the imaginary part [tex]\( b \)[/tex]:
[tex]\[ a = -3, \quad b = 2 \][/tex]

2. Substitute [tex]\( a \)[/tex] and [tex]\( b \)[/tex] into the magnitude formula:
[tex]\[ |z| = \sqrt{(-3)^2 + (2)^2} \][/tex]

3. Calculate [tex]\( (-3)^2 \)[/tex] and [tex]\( 2^2 \)[/tex]:
[tex]\[ (-3)^2 = 9, \quad 2^2 = 4 \][/tex]

4. Add these results together:
[tex]\[ 9 + 4 = 13 \][/tex]

5. Take the square root of the sum:
[tex]\[ |z| = \sqrt{13} \][/tex]

Therefore, the magnitude [tex]\( |z| \)[/tex] of the complex number [tex]\( z = -3 + 2i \)[/tex] is [tex]\( \sqrt{13} \)[/tex].

The correct answer is:
[tex]\[ \sqrt{13} \][/tex]