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Simplify the following complex fraction:

[tex]\[ \frac{5 + 6i}{3 - 4i} \][/tex]

A. [tex]\[ -\frac{9}{25} - \frac{38}{25}i \][/tex]

B. [tex]\[ -\frac{9}{25} + \frac{38}{25}i \][/tex]

C. [tex]\[ \frac{9}{25} - \frac{38}{25}i \][/tex]

D. [tex]\[ \frac{9}{25} + \frac{38}{25}i \][/tex]


Sagot :

To solve the problem [tex]\(\frac{5+6i}{3-4i}\)[/tex], we need to simplify the given complex fraction. Here is a step-by-step solution:

1. Identify the given complex number and its conjugate:

We have the complex number [tex]\(\frac{5 + 6i}{3 - 4i}\)[/tex]. To simplify this, we will multiply both the numerator and the denominator by the conjugate of the denominator.

The conjugate of [tex]\(3 - 4i\)[/tex] is [tex]\(3 + 4i\)[/tex].

2. Multiply the numerator and the denominator by the conjugate of the denominator:

[tex]\[ \frac{5 + 6i}{3 - 4i} \times \frac{3 + 4i}{3 + 4i}. \][/tex]

3. Perform the multiplication in the numerator:

Using the distributive property (FOIL):

[tex]\[ (5 + 6i)(3 + 4i) = 5 \cdot 3 + 5 \cdot 4i + 6i \cdot 3 + 6i \cdot 4i. \][/tex]

Simplify the terms:

[tex]\[ = 15 + 20i + 18i + 24i^2. \][/tex]

Recall that [tex]\(i^2 = -1\)[/tex]:

[tex]\[ = 15 + 20i + 18i + 24(-1). \][/tex]

[tex]\[ = 15 + 38i - 24. \][/tex]

[tex]\[ = -9 + 38i. \][/tex]

4. Perform the multiplication in the denominator:

[tex]\[ (3 - 4i)(3 + 4i) = 3 \cdot 3 + 3 \cdot 4i - 4i \cdot 3 - 4i \cdot 4i. \][/tex]

Simplify the terms:

[tex]\[ = 9 + 12i - 12i - 16i^2. \][/tex]

[tex]\[ = 9 + 0 - 16(-1). \][/tex]

[tex]\[ = 9 + 16. \][/tex]

[tex]\[ = 25. \][/tex]

5. Combine the results:

Now, we have:

[tex]\[ \frac{-9 + 38i}{25}. \][/tex]

Separate the real and imaginary parts:

[tex]\[ = -\frac{9}{25} + \frac{38}{25}i. \][/tex]

6. Match with the provided options:

The simplified form matches the option [tex]\(-\frac{9}{25} + \frac{38}{25}i\)[/tex].

So, the correct answer is:

[tex]\[ -\frac{9}{25} + \frac{38}{25}i \][/tex]