Question

How do you write in vertex form for `y=x^2 - 9x` by completing the square?

Answer 1

Given
`y=x^2-9x`

Completing the square
`y=x^2-9x+(9/2)^2 - (9/2)^2`

`y = (x-9/2)-81/4`
which is the vertex form with the vertex at `(9/2,-81/4)`