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

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Answer 1 · 2015-11-29T18:17:40

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

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

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

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