Consider polynomial \(x^3 - 4x^2 + 7x - 28.\) You can group first two terms and last two terms:
\(x^3 - 4x^2 + 7x - 28=(x^3 - 4x^2) + (7x - 28).\)
In first brackets the common factor is \(x^2\) and in second brackets the common factor is 7, then
\(x^3 - 4x^2 + 7x - 28=(x^3 - 4x^2) + (7x - 28)=x^2(x-4)+7(x-4)=(x-4)(x^2+7).\)
Answer: the correct answer is D.
