# How do you solve #x^2+4x=21#?

##### 2 Answers

Apr 8, 2017

#### Answer:

#### Explanation:

let

Moving the 21 to the other side we get

Now, we want two numbers that multiply to give -21 and and to give 4

These two numbers are 7 and -3.

7 x -3 = 21

7+-3 = 4

Factorizing this we get:

Now we make both brackets equal to zero

Apr 8, 2017

#### Answer:

See below.

#### Explanation:

We move everything onto one side, and factor.