Question

Find the vertex of the parabola and indicate if it is a minimum or maximum for the function f(x) = 3(x - 8)2 + 9 A. vertex at (-8, -9) is a maximum B. vertex at (8, 9) is a maximum C. vertex at (-8, -9) is a minimum D. vertex at (8, 9) is a minimum

Answer 1

D

Explanation:

The equation of a parabola in vertex form is

y = a(x - h)² + k

where (h, k) are the coordinates of the vertex and a is a multiplier

f(x) = 3(x - 8)² + 9 is in this form with (h, k) = (8, 9)

• If a > 0 then vertex is a minimum

• If a < 0 then vertex is a maximum

here a = 3 hence

vertex (8, 9 ) is a minimum → D

Answer 2

Explanation:

Sometimes the best thing you can do with this kind of question is just to graph it. The graph is below. Done on Desmos. It shows that the min is at (8,9)

So the answer is B.