a^2-13a+36=0
First we need to find 2 numbers that add to make 13 and multiply to make 36: factor pairs of 36 are: 1,36 2,18 3,12, 4,9 6,6
4 and 9 add to make 13 so those are the numbers we'll use:
(a-4)(a-9)=0
Now we check:
a*a+a*-9-4*a-4*-9=0
a^2-9a-4a+36=0
a^2-13a+36
Add 13a to both sides:
a^2+36=13a
So it works and the final answer is:
(a-4)(a-9)=0
Hope this helps :)