# How do you factor #x^2 + 4xy - 5y^2#?

##### 3 Answers

#### Explanation:

All the information you need is in the expression.

Read from right to left.

Find the factors of 5 which subtract to give 4.

The signs will be different (because of the **minus**), there will be more **positives** (because of +)

5 is a prime number - the only factors are 1 x 5 and we see 5 -1 = 4.

We need +5 and -1 to give +4

This leads to the two brackets:

#### Explanation:

So

so we have

We have three equations and four incognitas. Solving for

applying a feasible value for