# How do you factor 2x ^ { 2} + 21x = - 40?

##### 1 Answer
Apr 6, 2018

the answer is x=-8 & x=-5/2

#### Explanation:

first add $40$ to both sides to make it equal to $0$ and now you get $2 {x}^{2} + 21 x + 40 = 0$ now find two numbers that multiply to give you $80 \left(2 \cdot 40\right)$ and add to give you $21$ you get $16 , 5$ and now you put it in $2 {x}^{2} + 16 x + 5 x + 40 = 0$ now group then and take out what you can and you'll get $2 x \left(x + 8\right) + 5 \left(x + 8\right)$ the two parenthesis have to be the same. now you have $\left(2 x + 5\right) \left(x + 8\right)$ but since it's equal to $0$, you have to solve. so now you set them both to $0$ and you just solve for $x$ and you get your answer