Question #N780
The equation $2x^2 - 8x + c = 0$ has exactly one solution. What is the value of *c*?
A. 8
B. 16
C. -8
D. -16
Correct Answer is: B
A quadratic equation has exactly one solution when its discriminant is equal to zero. The discriminant of $ax^2 + bx + c = 0$ is $b^2 - 4ac$. In this equation, $a = 2$, $b = -8$, and $c = c$. Setting the discriminant equal to zero gives $(-8)^2 - 4(2)(c) = 0$, or $64 - 8c = 0$. Solving for $c$ yields $c = 8$. The correct answer is 8.