Resposta:

a) (2x-4)^2= (2x)^2-2x.4+4^2= 4x^2-16x+16

R=4x^2-16x+16

b) A=1,B=-1,C=-6

Δ=(-1)^2-4.1 (-6)

Δ= 1+24

Δ=25

X= -(-1) +√25

_______

2.1

X= 1+5

___

2

X' = 6

__ =3

2

X'' = -4

___ = -2

2

S= {-2,3}