Question

The roots of a quadratic equations are 2 and 4. Which one of the following quadratic equations has these roots?

Answer 1

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.