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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 :

Certainly! Let's analyze the given complex numbers and find their absolute values to determine which one has an absolute value of 5.

A complex number is given in the form [tex]\( a + bi \)[/tex], where [tex]\( a \)[/tex] is the real part and [tex]\( b \)[/tex] is the imaginary part. The absolute value (or modulus) of a complex number [tex]\( a + bi \)[/tex] is calculated using the formula:

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

Now, let's find the absolute values of the given complex numbers:

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

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

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

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

Among the given complex numbers, we see that the absolute value of the complex number [tex]\(-3 + 4i\)[/tex] is 5.

Therefore, the complex number [tex]\(-3 + 4i\)[/tex] has an absolute value of 5.