Question

Resolva : x(2x+4)=5(x+3)

Answer 1

x(2x+ 4) = 5(x + 3)
2x² + 4x = 5x + 15
2x² + 4x - 5x - 15 = 0
2x² -x - 15 = 0

a = 2
b = -1
c = -15

Δ = b² -4 .a . c

Δ = (-1)² -4 . 2 . (-15)
Δ = 1 - 8 . (-15)
Δ = 1 + 120
Δ = 121

-b +- √Δ    /2.a
-(-1) +- √ 121    / 2 . 2
1 +- 11   /4

x' = 1 + 11   /4
x' = 12 / 4
x' = 3

x'' = 1 - 11  /4
x'' = -10  /4    (÷2)
x'' =  -5/2

Resposta : S{ -5/2 , 3}