Posted by **Claure** on Tuesday, June 16, 2009 at 7:57pm.

f(x)=x^3-4x^2-x+4

How do I find the x-intercept for this?

This is from my book:

step 1: 0=x^3-4x^2-x+4

step 2: 0=x^2(x-4)+(-1)(x-4)

step 3: 0=(x^2-1)(x-4)

I know how to solve once I get to step 3, but in step 2, I don't know what they've done or why. Where does that (-1) come from? Why is it (x-4)?

Please help explain this to me. I'd be really thankful.

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