Question

Which of the following equations has only one solution?
x2 + 4x + 4 = 0
x2 + x = 0
x2 - 1 = 0

Answer 1

x^2 + 4x + 4 = 0
(x+2)^2 = 0
x+2 = 0
x = -2

answer
this one has only one solution

Answer 2

The answer is the first one. 

1) x = {-2}
2) x = {0, -1}
3) x = {1, -1}

The first one only has one solution