Practice free →
HomeGRE › Quantitative Reasoning › How many **real solutions** does the equation $x…

How many **real solutions** does the equation $x^{2} + 4x + 4 = 0$ have, and what are they?

ATwo: $x = 2$ and $x = -2$
BTwo: $x = 4$ and $x = -1$
COne: $x = -2$ (a double root)
DNone
Answer & Solution
Correct answer: C. One: $x = -2$ (a double root)
The discriminant determines how many real solutions a quadratic has: $\Delta = b^{2} - 4ac = 4^{2} - 4(1)(4) = 16 - 16 = 0$. When $\Delta = 0$, there is exactly **one** real solution (a repeated root): $x = \dfrac{-b}{2a} = \dfrac{-4}{2} = -2$. Confirm by factoring: $x^{2} + 4x + 4 = (x + 2)^{2}$. Setting $(x + 2)^{2} = 0$ gives $x = -2$ as the only solution. Three-case rule for the discriminant: $\Delta > 0$ → two distinct real roots; $\Delta = 0$ → one repeated root; $\Delta < 0$ → no real roots.
Solve this in the app — GRE practice & 24k+ MCQs →
Related questions