Question

Factor x2 + 9 in the complex numbers.

A) (x + 3)(x - 3)
B) (x + 3)(x + 3)
C) (x + 3i)(x - 3i)
D) (x + 3i)(x + 3i)

Answer 1

C) (x + 3i)(x - 3i)

Explanation:

(x + 3i)(x - 3i)

=x² - (3i)² [(a+b)(a-b)=a²-b²]

=x² - 9i²

=x² - 9(-1) [i²=-1]

= x² + 9

Answer 2

Good evening ,

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Answer:

The right answer is C

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Explanation:

x² + 9 = x² − (−9) = x² − (i²×9) = x² − i²× 3² = x² − (3i)² = (x + 3i)(x - 3i).

:)