Plug in -12 for [tex]f(x)[/tex]!
[tex]-12=x^{2}-x-12[/tex]
Now get the left side equal to zero so you can factor:
[tex]0=x^{2}-x[/tex]
Now you can factor out an [tex]x[/tex]!
[tex]0=x(x-1)[/tex]
So for that to equal zero, [tex]x=0[/tex] or [tex]x=1[/tex]!
