posted by Elisa on .
Andrew factored the expression -12x^3-28x^2-3x as -4x (3x^2-7x+9). But when Melissa applied the distributive law and multiplied out -4x (3x^2-7x+9), she got -12x^3+28x^2-36x; thus, Andrew’s solution does not appear to check. Why is that? Please help Andrew to understand this better. Explain your reasoning and correctly factor the original expression, if possible. If the expression is prime, so state.
Given: -12X^3 - 28X^2 - 3X.
Andrew made 2 mistakes:
1. You can't factor out -4x, because -3
is not divisible by -4.
2.The 2nd term in the parenthesis should be +7X.
You can only factor out an X:
X(-12X^2 - 28X - -3).