Question

X elevado a 2 menos x menos 20 igual a zero

Answer 1

Equaçao de segundo grau ! Resolvendo delta ( b² - 4ac ) sendo b = -1 , a = 1 e c = -20 . Você vai encontrar delta igual a 81.

Depois faz .... x = -b +/- raiz de delta dividido por 2a
 x = 1+/- 9 dividido por 2
x' = 5 e x " -4

:)

Answer 2

$x^{2} -2x-20=0\\\\ a=1;b=-2;c=-20\\\\\\ \Delta= b^{2} -4ac \to \Delta= (-2)^{2}-4*1*(-20) \to \Delta=4+80 \to \Delta= 84\\\\\\ x= \frac{-b+- \sqrt{\Delta} }{2a} \to x= \frac{-(-2)+- \sqrt{84} }{2*1} \to x= \frac{2+-9,16 }{2} \to \\\\\\ x'= \frac{2+9,16 }{2} \to x'= \frac{11,16 }{2} \to x'= 5,58\\\\\\ x''= \frac{2-9,16 }{2} \to x''= \frac{-7,16 }{2} \to x''= -3,58\\\\\\ S=(-3,58;5,58)$