Question

What is the the vertex of `y = 7x^2 - 9x`?

Answer 1

The vertex is the point `(9/14, -81/28)`

Explanation:

The vertex of such a parabola is the minimum of the parabola. So, we can derive the equation to obtain

`14x-9`

To seek a maximum, set the derivative to zero:

`14x-9=0 \iff 14x=9 \iff x=9/14`

So, the `y` coordinate of the maximum is

`7(9/14)^2 - 9 (9/14) = -81/28`