Question

resolve as seguintes equações de 2 grau:
x²+4x-5=0

Answer 1

Δ = 16 + 20 
Δ = 36 

x = -4 +-√36/2
x = -4 +-6/2

x' = -4+6/2
x' = 2/2 = 1

x'' = -4-6/2
x'' = -10/2 = -5                     S = { -5 , 1 }              ok

Answer 2

a=1
b=4
c=-5

∆=b^2-4ac

∆=(4^2= 16) -4.1.(-5)
∆=16+20
∆=36

x= -b+-√∆/a.2
x=-(4)+-√36/1.2
x=-4+-6/2
x1=-4+6/2= 2/2: 1
x2=-4-6/2=-10/2= -5

S={-5,1}