Question

5) Quais são as raízes da equação x2-3x-4=0?​

Answer 1

Explicação passo-a-passo:

$\sf x^2-3x-4=0$

$\sf \Delta=(-3)^2-4\cdot1\cdot(-4)$

$\sf \Delta=9+16$

$\sf \Delta=25$

$\sf x=\dfrac{-(-3)\pm\sqrt{25}}{2\cdot1}=\dfrac{3\pm5}{2}$

$\sf x'=\dfrac{3+5}{2}~\Rightarrow~x'=\dfrac{8}{2}~\Rightarrow~\red{x'=4}$

$\sf x"=\dfrac{3-5}{2}~\Rightarrow~x"=\dfrac{-2}{2}~\Rightarrow~\red{x"=-1}$

As raízes são 4 e -1