Question

equação do grau
x ao quadrado -8x -9=0​

Answer 1

${x}^{2} - 8x - 9 = 0 \\ \Delta = {b}^{2} - 4ac \\ \Delta = {( - 8)}^{2} - 4.1.( - 9) \\ \Delta = 64 + 36 \\ \Delta = 100$

$x = \frac{-b±\sqrt{\Delta} }{2a} \\ x = \frac{ - ( - 8)± \sqrt{100} }{2.1} \\ x = \frac{8±10}{2}$

$x' = \frac{8 + 10}{2} = \frac{18}{2} = 9 \\ x'' = \frac{8 - 10}{2} = - \frac{2}{2} = - 1$

S={-1,9}