SOLUTION: Which of the following expressions is equal to -3x^2-27 A ) (-3x-3i)(x-9i) B ) (-3x-9i)(x+3i) C ) (-3x+3i)(x+9i) D ) (-3X+9i)(x+3i) i know i have to factor (i think) to solve

Question 1082119: Which of the following expressions is equal to -3x^2-27
A ) (-3x-3i)(x-9i)
B ) (-3x-9i)(x+3i)
C ) (-3x+3i)(x+9i)
D ) (-3X+9i)(x+3i)
i know i have to factor (i think) to solve it but i'm having trouble when it comes to getting the final form ( cant think of the right term)
Found 3 solutions by Boreal, math_helper, MathLover1:
Answer by Boreal(15235)   (Show Source): You can put this solution on YOUR website!
it is -3(x^2+9)=or -3(x+/-3i)=-3(x+3i)(x-3i)
-3x+9i could be one factor with (x+3i), -3x-9i could be another with (x-3i).
D works.
-3(x-3i)(x+3i)
Answer by math_helper(2461)   (Show Source): You can put this solution on YOUR website!
Three criteria must be met:
1) the factors must multiply to give a -3x^2 terms (all of therm do)
2) the factors must multiply such that the xi terms cancel (NOT all of them do)
3) the factors must multiply to give -27 (= +27i^2 because i^2 = -1) (NOT all of them do)
I'll add that A) is NOT correct because �> which has a term.

Scroll down for answer.

D:
Answer by MathLover1(20849)   (Show Source): You can put this solution on YOUR website!

........here we have the sum of squares and we can write it as the difference of squares if we write as , and we know that ; so, we have or
now factor it as the difference of the squares and you have
plug it in:
....multiply

answer:
D )
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