Question

Help with maximum and minimum?

Answer 1

I have to find the x coordinate of the vertex of this quadratic function: y = 2/27x^2 - 4/3x

I used the formula to find the x-coordinate:

x = -b/2a
x = (-4/3)/(2 * 2/27)
x = (-4/3)/(4/27)
x = -9

But when I graphed the function to check, I found the vertex is not -9, it's 9. I don't know what I did wrong here, can someone please explain?

Answer 2

there is an error in the second line
-b = -(-4/3) = 4/3

Answer 3

ok?

Answer 4

b is -4/3 in your function so -b = -(-4/3)

Answer 5

Oh, ok.

Answer 6

standard is
y = ax^2 + bx + c

compare
y = a x^2 + bx = c
y = 2/27 x^2 - 4/3 x

Answer 7

a = 2/27 and b = -4/3

Answer 8

yw

Answer 9

Thanks for your help:)