Resposta:

f(x) = x²+2x+1

a = 1

b = 2

c = 1

Δ= b² -4ac

Δ = 2² -4.(1)(1)

Δ = 4 - 4

Δ = 0

[tex]x=\dfrac{-b\pm\sqrt{\Delta} }{2a}\\ \\ \\ x=\dfrac{-2\pm\sqrt{0} }{2.(1)}=\dfrac{-2\pm0}{2}=\dfrac{-2}{2}=-1\\\\ \\\boxed{ x'=x"=-1}[/tex]