Question

 Me ajuda  resolver a equação- x² + 10x - 21 =0

Answer 1

(Delta) = (-10)² - 4 . 1 . 21
(Delta)= 100 - 84
(Delta)= 16

x = - (-10) +- √16 / 2 . 1

x = 10 +- 4 / 2

x' = 14/2 = 7

x'' = 6/2 = 3

R: {7, 3}

Answer 2

$- x^{2} +10x-21=0 \\ \\ a=-1 \\ b=10 \\ c=-21 \\ \\ \Delta=b^2-4ac \\ \Delta=10^2-4(-1)(-21) \\ \Delta=100-84 \\ \Delta=16 \\ \\ x= \frac{-b\pm \sqrt{\Delta} }{2a} = \frac{~-10\pm \sqrt{16} }{-2} = \frac{-10\pm4}{-2} \\ \\ x'= \frac{-10+4}{-2} = \frac{-6}{-2} =+3 \\ \\ x"= \frac{-10-4}{-2} = \frac{-14}{-2} =+7 \\ \\ S=\{3,7\}$