SOLUTION: Factor completely. {{{ 7x^3-4x^2-8x }}} **So far I have factored an x out of all terms {{{ x(7x^2-4x-8) }}} I am not sure how to factor the rest

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Factor completely. {{{ 7x^3-4x^2-8x }}} **So far I have factored an x out of all terms {{{ x(7x^2-4x-8) }}} I am not sure how to factor the rest      Log On


   

Question 484553: Factor completely.
+7x%5E3-4x%5E2-8x+
**So far I have factored an x out of all terms
+x%287x%5E2-4x-8%29+
I am not sure how to factor the rest
Found 2 solutions by stanbon, jorel1380:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
7x^3-4x^2-8x
----
= x(7x^2-4x-8)
---
There is no further factoring
which would simplify the form.
=======================
Cheers,
Stan H.

Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
x(7x^2-4x-8)=
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 7x%5E2%2B-4x%2B-8+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-4%29%5E2-4%2A7%2A-8=240.

Discriminant d=240 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--4%2B-sqrt%28+240+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-4%29%2Bsqrt%28+240+%29%29%2F2%5C7+=+1.39228095605926
x%5B2%5D+=+%28-%28-4%29-sqrt%28+240+%29%29%2F2%5C7+=+-0.820852384630691

Quadratic expression 7x%5E2%2B-4x%2B-8 can be factored:
7x%5E2%2B-4x%2B-8+=+7%28x-1.39228095605926%29%2A%28x--0.820852384630691%29
Again, the answer is: 1.39228095605926, -0.820852384630691. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+7%2Ax%5E2%2B-4%2Ax%2B-8+%29

So the answer is 1.39228095605926(x) or -0.820852384630691(x)