Browse · MATH Print → jmc algebra intermediate Problem The solution to the inequality y=−x2+ax+b≤0is (−∞,−3]∪[5,∞). Find the vertex of the parabola y=−x2+ax+b. Solution — click to reveal The roots of the quadratic are −3 and 5, so y=−x2+ax+b=−(x+3)(x−5)=−x2+2x+15=−(x−1)2+16.Thus, the vertex is (1,16). Final answer (1,16) ← Previous problem Next problem →