assuming [tex] \sqrt{3x+12} =x[/tex] sqare both sides 3x+12=x² minus 3x+12 both sides x²-3x-12=0 factor we can't use quadratic formula for ax²+bx+c=0 [tex]x= \frac{-b+/- \sqrt{b^2-4ac} }{2a} [/tex] so
[tex]x= \frac{-(-3)+/- \sqrt{(-3)^2-4(1)(-12)} }{2(1)} [/tex] simplfying we get [tex]x= \frac{3+ \sqrt{57} }{2} [/tex] or [tex]x= \frac{3- \sqrt{57} }{2} [/tex]
