Step-by-step explanation:
[tex]\sqrt{12-8x} =x-3\\[/tex]
square both sides
[tex]12-8x=(x-3)^2[/tex]
expand
[tex]12-8x=x^2-6x+9[/tex]
simplify
0=x^2+2x-3
Factor
0=(x+3)(x-1)
the possible values for x are -3 and 1
Hope that helps :)
