So to solve this, you want to factor it.
Start by looking at items that multiply to -2 and add to -1
We can see that the numbers are -2 and 1, so now put each one in a term
(x-2)(x+1) = 0
Now, to solve it set it to 0 and say x+1 = 0 and x-2 = 0
so x = -1 and 2
[tex] x^2 - x - 2 = 0\\x^2+x-2x-2=0\\x(x+1)-2(x+1)=0\\(x-2)(x+1)=0\\x=2\vee x=-1 [/tex]