Answer:
It must be a perfect square. You can try factoring each equation to see if you have a perfect square, or you can evaluate the discriminant of each one. If the discriminant is zero, there is one real root to the equation. Try this approach.
f(x) = ax2 + bx + c
D = b2 - 4ac
If D = 0, then there is exactly one root, and it is real.
