Answer: B
Step-by-step explanation:
You can factor out a 5x² from each of the terms leaving you with:
5x²(x² + 4x - 21)
the term in the parenthesis can be factored down even more. You need to find two numbers whos sum is equal to 4 but when multiplied together equals -21. 7 and -3 fit this as 7 x -3 = -21 and 7 + (-3) = 4 so the factored form of the term in the parenthesis above would then be:
(x+7)(x-3)
So we can then substitute that in for the term in the parenthesis and we get the final answer of:
5x²(x+7)(x-3)
