Question

(2 x + 4) ( x + 5)=0

Answer 1

$\mathtt{Distributiva} \\ \\ \mathtt{(2x+4)~.~(x+5) = 0} \\ \mathtt{2x^2 + 10x + 4x + 20 = 0} \\ \mathtt{2x^2 +14x + 20 = 0} \\ \\ \mathtt{a = 2} \\ \mathtt{b = 14} \\ \mathtt{c = 20} \\ \\ \mathtt{\Delta = b^2 -4~.~a~.~c} \\ \\ \mathtt{\Delta = 14^2-4~.~2~.~20} \\ \mathtt{\Delta =196-8~.~20 } \\ \mathtt{\Delta = 196 -160 } \\ \mathtt{\Delta= 36 } \\ \\ \\ \mathtt{\dfrac{-b +- \sqrt{\Delta}}{2~.~a}} \\ \\ \\ \mathtt{\dfrac{-14 +- \sqrt{36}}{2~.~2}} \\ \\ \\ \mathtt{\dfrac{-14 +- 6}{4}}$


$\mathtt{x' = \dfrac{-14 +6}{4}~~=~~~x' = -\dfrac{8}{4} ~=~~~~ \boxed{x' =-2 }} \\ \\ \\ \mathtt{x" = \dfrac{-14 - 6}{4}~= ~~~~~x" = -\dfrac{20}{4}~=~~~~~\boxed{x" =-5 }} \\ \\ \\ \boxed{\boxed{\mathtt{Resposta : S\{-2~~,~~-5\} }}}$

Answer 2

Olá, boa noite ☺

Resolução:

(2x + 4) ( x + 5)=0
2x²+10x+4x+20=0
2x²+14x+20=0

Coeficientes:

a=2, b=14, c=20

Valor do discriminante:

Δ=b²-4.a.c
Δ=14²-4.2.20
Δ=196-160
Δ=36

Valores de x:

x=-b±√Δ/2.a
x=-14±√36/2.2
x=-14±6/4

x'=-14+6/4=-8/4=-2
x''=-14-6/4=-20/4=-5

S={-2,-5}

Bons estudos :)