Question

Calcule mentalmente as raizes de equacao x²-x-12=0

Answer 1

Δ = $(-1)^{2} - 4.(1).(-12) = 1+ 48 = 49\\\\X= \frac{-(-1)+- \sqrt{49} }{2.(-1)} \\\\X'= \frac{1+7}{-2} = \frac{8}{-2} =-4\\\\X''= \frac{1-7}{-2} = \frac{6}{-2}=-3$