Question

Qual é a raiz de x²-3x-4=0 ?

Answer 1

x² - 3x - 4 = 0     a) 1   b) - 3    c) - 4
Δ = b² - 4 . a . c
Δ = -3² - 4 . 1 . -4
Δ = 9 + 16
Δ = 25

- b +/- √Δ / 2 . a
- ( - 3 ) +/- √25 / 2 . 1
3 +/- 5 / 2
x' = 3 + 5 /2 = 8/2 = 4
x'' = 3 - 5 / 2 = - 2/2 = - 1

Answer 2

Resposta:

S = {- 1, 4}

Explicação passo-a-passo:

$x^{2} -3x-4=0$

$a=1\\b=(-3)\\c=(-4)$

$\Delta=b^{2} -4ac\\\Delta=(-3)^{2} -4\times1\times(-4)\\\Delta=9+16\\\Delta=25$

$x=\frac{-b\pm\sqrt{\Delta} }{2a} \\\\x=\frac{-(-3)\pm\sqrt{25} }{2\times1} \\\\x=\frac{3\pm5}{2}$

$x_{1} =\frac{3+5}{2} =\frac{8}{2} =4\\\\x_{2} =\frac{3-5}{2} =-\frac{2}{2} =-1$