Question

x ao quadrado menos 2X menos 3 igual a zero

Answer 1

x² - 2x - 3 = 0

a = 1          b = - 2          c = - 3

Δ = b² - 4ac
Δ = (-2)² - 4.(1).(-3)
Δ = 4 + 12
Δ = 16

$x = \frac{-b \frac{+}{-} \sqrt{b^2-4ac} }{2a}$

$x = \frac{-(-2) \frac{+}{-} \sqrt{16} }{2}$

$x = \frac{2 \frac{+}{-} 4 }{2}$

$x' = \frac{2+4}{2}$

$x' = \frac{6}{2}$

$x' = 3$

$x" = \frac{2-4}{2}$

$x" = \frac{-2}{2}$

$x" = - 1$

S = {-1,3}