
First you should ask, which two numbers add up to -10 and multiply to 9.
-9 and -1 add up to -10 and multiply to 9.


So we can factor and rewrite like this ;

Let's equal it to 0 again.

The multiplication of (x-9) and (x-1) is equal to 0
So we should equal them to 0 seperately to find the solution set

and

The solution set,
