Question #N912
The equation $x^2 - 6x + k = 0$ has exactly one solution. What is the value of $k$?
A. 9
B. -9
C. 36
D. -36
Correct Answer is: A
A quadratic equation has exactly one solution when its discriminant is equal to 0. The discriminant of the quadratic equation is , where a, b, and c are the coefficients of the quadratic equation. In this equation, a=1, b=-6, and c=k. Substituting these values into the discriminant formula yields . Setting the discriminant equal to zero yields , or k = 9.