### Home > A2C > Chapter 7 > Lesson 7.1.3 > Problem7-41

7-41.

Factor each expression completely. Homework Help ✎

1. $25x^2-1$

This is a difference of two squares.

If you don't know the pattern for difference of two squares yet, use a generic rectangle to help you.

$(5x+1)(5x−1)$

1. $5x^3-125x$

$5x$ is a common factor. Factor it out. What is left is a difference of two squares, as in part (a). Factor again.

$5x(x+5)(x−5)$

1. $x^2+x-72$

You can use an area model.

1. $x^3-3x^2-18x$

The common factor is $x$.

After you factor out $x$ you have to factor a second time.