If x^2 + mx + m is a perfect-square trinomial, which equation must be true?
x^2 + mx + m = (x – 1)^2
x^2 + mx + m = (x + 1)^2
x^2 + mx + m = (x + 2)^2
x^2 + mx + m = (x + 4)^2

Question

If x^2 + mx + m is a perfect-square trinomial, which equation must be true?
x^2 + mx + m = (x – 1)^2
x^2 + mx + m = (x + 1)^2
x^2 + mx + m = (x + 2)^2
x^2 + mx + m = (x + 4)^2

abb0t · Answer

You can clearly cancel 2 of those choices, since you know $\sf \color{}{ax^2+bx+c}$ since your $C$ vvalue = 1 and it makes no sense to have 2 or 4 as your C value. 
So you're left with choices A or B.