Question

X(X-9)=-20
Qual é o resultado?

Answer 1

x(x - 9) = -20

x² - 9x = -20

x² - 9x + 20 = 0

$x=\frac{-(-9) \pm \sqrt{(-9)^{2}-4 \times 1 \times 20 } }{2 \times 1}$

$x=\frac{9 \pm \sqrt{81-80} }{2}$

$x=\frac{9 \pm \sqrt{1} }{2}$

$x=\frac{9 \pm 1}{2}$

$x_1 = \frac{9+1}{2}\\ x_2= \frac{9-1}{2}$

$x_1= 5\\x_2 = 4$