Q:

Which of the following expressions is equal to 3x^2+27

Accepted Solution

A:
Factor: 
3x^2 + 27
= 3(x^2  + 9)
Answer is 3(x^2 + 9), when factored.


A) (3x + 9i)(x + 3i)
= (3x + 9i)(x + 3i)
= (3x)(x) + (3x)(3i) + (9i)(x) + (9i)(3i)
= 3x^2 + 9ix + 9ix + 27i^2
= 27i^2 + 18ix + 3x^2



B) (3x - 9i)(x + 3i)
= (3x +  - 9i)(x + 3i)
= (3x)(x) + (3x)(3i) + ( - 9i)(x) + (- 9i)(3i)
= 3x^2 + 9ix - 9ix - 27i^2
= 27i^2 + 3x^2


C) (3x - 6i)(x + 21i)
= (3x +  - 6i)(x + 21i)
= (3x)(x) + (3x)(21i) + (- 6i)(x) + ( -6i)(21i)
= 3x^2 + 63ix - 6ix - 126i^2
=  - 126i^2 + 57ix + 3x^2






D) (3x - 9i)(x - 3i)
=  (3x +   - 9)(x +  - 3)
= (3x)(x) + (3x)( - 3i) + (- 9)(x) + ( - 9)( - 3i)
= 3x^2 - 9ix - 9x + 27i
= 9ix + 3x^2 + 27i - 9x









Hope that helps!!!