Homework Help: Algebra help

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.

Algebra help - Damon, Tuesday, June 16, 2009 at 8:07pm
step 1: 0=x^3-4x^2-x+4

we would like to factor that.
rewrite as
x^3-4x^2 - (x-4)
now you can see that I can factor an (x-4) out of the first two terms
x^2 (x-4) - (x-4)
which is
x^2 (x-4) -1 (x-4)

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

Answer this Question

Related Questions

MATH - A student is solving the equation 81x – 1 = 3x + 2. Step 1: 81x &#...
Algebra - 27-f(x)=1/4x^2-2x-12. Can you show me how to find the vertex and x ...
Algebra - Can you pleas Solve the quadric equation step by step 4x square =13x+...
Algebra - 4x^4-18x^2=0. I have to find out what x equals by factoring. What I ...
Pre-calculus - can someone show how to graph step by step the polynomial ...
Alg 2 - Find the lcd 14/4(x+1) , 7/4x I don't get it can you please explain...
Algebra - How do you factor a quartic equation such as 4x^3-24x^2-x+6. Could you...
Math - Find the maximum or minimum value: -x^2+2x+5 3x^2-4x-2 can someone ...
math/algebra - solve each of the following systems by substitution. 16) 5x -2y...
calculus - How do you find the derivative of (-2(x^2+1))/((x^2-1)^2) ? I have ...

For Further Reading

First Name:
School Subject:
Answer: