Finding the value of x given y is a maximum? See picture below

enter image source here

1 Answer
Apr 9, 2017

When given an equation of the form y=ax2+bx+c, where "a" is negative, the maximum value is the y coordinate of the vertex. The x coordinate of the vertex is:
h=b2a

Explanation:

Given: y=16x2+160x256

We observe that a=16 and b=160

The x coordinate of the vertex is:

h=b2a

h=1602(16)

h=5 this is the answer to [7.a.i]

The maximum value is the function evaluated at x=h=5:

y=16(5)2+160(5)256

y=144 this is the answer to [7.a.ii]