SOLUTION: What is the factorization of the polynomial below? x3 + 3x2 - 40x

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Question 393221: What is the factorization of the polynomial below?
x3 + 3x2 - 40x
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
First I'll factor out x
x%2A%28x%5E2+%2B+3x+-+40%29
I'll use the quadratic formula to factor the 2nd term
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a+=+1
b+=+3
c+=+-40
x+=+%28-3+%2B-+sqrt%28+3%5E2-4%2A1%2A%28-40%29+%29%29%2F%282%2A1%29+
x+=+%28-3+%2B-+sqrt%28+9+%2B+160+%29%29+%2F+2+
x+=+%28-3+%2B-+sqrt%28+169+%29%29+%2F+2+
x+=+%28-3+%2B13%29%2F2%0D%0A%7B%7B%7Bx+=+5
and
x+=+%28-3+-+13%29%2F2
x+=+-8
From finding the roots, I can say
x+-+5+=+0 and
x+%2B+8+=+0
The complete factorization is
x%2A%28x+-+5%29%2A%28x+%2B+8%29