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Which complex number has an absolute value of 5?

A. [tex] -3 + 4i [/tex]

B. [tex] 2 + 3i [/tex]

C. [tex] 7 - 2i [/tex]

D. [tex] 9 + 4i [/tex]


Sagot :

To find the complex number that has an absolute value of 5, let's analyze each of the provided options. The absolute value (or modulus) of a complex number [tex]\( a + bi \)[/tex] is given by the formula [tex]\( |a + bi| = \sqrt{a^2 + b^2} \)[/tex]. We will calculate the absolute value for each given complex number.

1. For [tex]\(-3 + 4i\)[/tex]:
[tex]\[ | -3 + 4i | = \sqrt{(-3)^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5 \][/tex]

2. For [tex]\(2 + 3i\)[/tex]:
[tex]\[ | 2 + 3i | = \sqrt{2^2 + 3^2} = \sqrt{4 + 9} = \sqrt{13} \approx 3.605 \][/tex]

3. For [tex]\(7 - 2i\)[/tex]:
[tex]\[ | 7 - 2i | = \sqrt{7^2 + (-2)^2} = \sqrt{49 + 4} = \sqrt{53} \approx 7.280 \][/tex]

4. For [tex]\(9 + 4i\)[/tex]:
[tex]\[ | 9 + 4i | = \sqrt{9^2 + 4^2} = \sqrt{81 + 16} = \sqrt{97} \approx 9.849 \][/tex]

From the calculations above, we see that the complex number [tex]\(-3 + 4i\)[/tex] has an absolute value of 5. Therefore, the complex number with an absolute value of 5 is:
[tex]\[ \boxed{-3+4i} \][/tex]