# Math Help - factorising

1. ## factorising

Factorise $m^2+9m+20$

I thought it would be $(m+10)(m-1)$ but that wouldn't work

2. Originally Posted by Mukilab
Factorise $m^2+9m+20$

I thought it would be $(m+10)(m-1)$ but that wouldn't work
Both your signs will be + since 9 and 20 are both greater than 0. Think about what other numbers multiply to make 20.

$20 = 1 \times 20 \: , 2 \times 10 , 4 \times 5$

From the above pick a pair that add up to 9

The answer is $(m+4)(m+5)$

3. $m^2+9m+20=(m+5)(m+4)$

4. Lol I am such an idiot >.<