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Select the correct answer.

Which complex number is equivalent to this expression?
[tex]\[ \frac{1}{3}(6+3i) - \frac{2}{3}(6-12i) \][/tex]

A. [tex]\(6 - 7i\)[/tex]
B. [tex]\(6 + 9i\)[/tex]
C. [tex]\(-2 - 7i\)[/tex]
D. [tex]\(-2 + 9i\)[/tex]


Sagot :

To determine the correct complex number equivalent to the given expression, [tex]\(\frac{1}{3}(6 + 3i) - \frac{2}{3}(6 - 12i)\)[/tex], we'll break it down step-by-step.

1. Calculate [tex]\(\frac{1}{3}(6 + 3i)\)[/tex]:
[tex]\[ \frac{1}{3}(6 + 3i) = \frac{1}{3} \cdot 6 + \frac{1}{3} \cdot 3i = 2 + i \][/tex]

2. Calculate [tex]\(\frac{2}{3}(6 - 12i)\)[/tex]:
[tex]\[ \frac{2}{3}(6 - 12i) = \frac{2}{3} \cdot 6 + \frac{2}{3} \cdot (-12i) = 4 - 8i \][/tex]

3. Subtract the two results:
[tex]\[ (2 + i) - (4 - 8i) \][/tex]

Now, distribute the subtraction:

[tex]\[ 2 + i - 4 + 8i = (2 - 4) + (i + 8i) = -2 + 9i \][/tex]

Therefore, the complex number equivalent to the given expression is [tex]\(-2 + 9i\)[/tex].

So, the correct answer is:
[tex]\[ \boxed{-2 + 9i} \][/tex]

And this matches with:
[tex]\[ \boxed{D} \][/tex]