61Vertex of a parabola

The graph of $\displaystyle y = 2x^2 - 12x + 11$ in the $\displaystyle xy$-plane has its vertex at $\displaystyle (h, k)$. What is the value of $\displaystyle k$? A) −25 B) −7 C) 3 D) 11

The vertex is at (3, −7), so k = −7, which is answer B. Using h = −b/2a = 12/4 = 3, then plugging x = 3 into the equation gives k = 18 − 36 + 11 = −7.