How long does it take an account with a principal of $300 to earn $81 in interest at a simple annual interest rate of 3%?

maximum at (4, 9)

Step-by-step 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

y = - 1(x - 4)² + 9 is in this form

with vertex = (4, 9)

• If a > 1 then vertex is a minimum

• If a < 0 then vertex is a maximum

here a = - 1 , hence vertex (4, 9) is a maximum