Question

Encontre as raízes da equaçâo x²-3x -4=0. *

-2 e 3
-1 e 6
-1 e 4
0 e 10
-1 e -5

Answer 1

$x^2 - 3x-4=0\\\Delta = (-3)^2 - 4 \cdot 1 \cdot (-4)\\\Delta = 9 - 4 \cdot (-4)\\\Delta = 9 + 16\\\Delta = 25\\\\x = \frac{-(-3)\pm \sqrt{25}}{2 \cdot 1} = \frac{3\pm5}{2}\\\\x_1 = \frac{3-5}{2} = -\frac{2}{2} = -1\\\\x_2 = \frac{3+5}{2} = \frac{8}{2} = 4\\\\\boxed{S = \{-1 \ e \ 4\}}$