Question

Resolva -x²-x+20=0 conta completa

Answer 1

$-x^2-x+20 = 0 \\ \\ a = -1 \\ b = -1 \\ c = 20 \\ \\ \Delta = b^2-4.a.c \\ \Delta = (-1)^2 - 4.(-1).20 \\ \Delta = 1 - (-80) \\ \Delta = 81 \\ \\ x = \frac{-b\pm \sqrt{\Delta} }{2.a} \\ \\ x = \frac{-(-1)\pm \sqrt{81} }{2.(-1)} \\ \\ x = \frac{1\pm9}{-2} \\ \\ \\ x' = \frac{1+9}{-2} \rightarrow x' = \frac{10}{-2} \rightarrow x' = -5 \\ \\ x'' = \frac{1-9}{-2} \rightarrow x'' = \frac{-8}{-2} \rightarrow x'' = 4$

Raízes:

$x' = -5 \\ x'' = 4$