Question

Find the maximum value of y = -x^2 + 6x + 5​

Answer 1

D

Explanation:

The maximum value is the y- coordinate of the vertex

Given a quadratic in standard form , y = ax² + bx + c ( a ≠ 0 )

Then the x- coordinate of the vertex is

x = -
`(b)/(2a)`

y = - x² + 6x + 5 ← is in standard form

with a = - 1 and b = 6 , then x- coordinate of vertex is

x = -
`(6)/(-2)` = 3

Substitute x = 3 into the function for y- coordinate of vertex

y = - 3² + 6(3) + 5 = - 9 + 18 + 5 = 14

maximum value is 14 → D

Answer 2

the answer is C, you use the formula x=-b/2a