Answer: I think that this is correct: x^4 - 8x^3 + 7x^2 - 28x + 28
Step-by-step explanation:
Take (x^2-4x)^2 and break it up to solve
(x^2-4x)(x^2-4x)=x^4-8x^3+16x
Then bring in the rest of the equation and add and subtract to solve
x^4-8x^3+16+7x^2-28x+12=x^4-8x^3+7x^2-28x+28
