# Maths question help ?

Solve by factorising x squared + 9x+20=0

### 15 Answers

- Engr. RonaldLv 74 months ago
x^2 + 9x + 20 = 0

(x + 4)(x + 5) = 0

x + 4 =0 , x + 5 = 0

x = - 4, x = - 5

x = - 4, - 5 answer//

- KrishnamurthyLv 74 months ago
x^2 + 9x + 20 = 0

x^2 + 5x + 4x + 20 = 0

x(x + 5) + 4(x + 5) = 0

(x + 5)(x + 4) = 0

Solutions:

x = -5

x = -4

- Anonymous4 months ago
I did it in my mind the answer

Solutions:

x = -5

x = -4

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- Ian HLv 74 months ago
Here is an explanation of how to do this example.

If you multiply out two factors such as (x + a)(x + b) you get

x^2 + (a + b)x + a*b,

so now compare that with your example

x^2 + 9x + 20 = 0

You need two numbers that add to make 9 and multiply to make 20.

That is easy, because 4 *5 = 20 and 4 + 5 = 9, so now you can write

x^2 + 9x + 20 = (x + 4)(x + 5) = 0

Either x + 4 = 0. which makes x = -4, or,

x + 5 = 0. which makes x = -5

You were expected to know this method already, so, I suggest that

you remember it now as it will be needed many times.

- Anonymous4 months ago
YOU ARE LAZY AND DISHONEST BY ASKING STRANGERS TO DO YOUR HOMEWORK. IF YOU TOLD YOUR TEACHER YOU DID IT YOU WOULD FAIL.

And you SHOULD FAIL as you are cheating.