Question

How do you write the quadratic in vertex form given `y= -3x^2 + 21x`?

Answer 1

`y = -3(x - 7/2)^2+147/4 = -3(x - 3.5)^2+36.75`

`y = -3x^2+21x = -3(x^2-7x)`
`= -3((x-(7/2))^2 - (7/2)^2)`
`= -3(x-(7/2))^2+3(7/2)^2`
`= -3(x - 7/2)^2+147/4`
`= -3(x - 3.5)^2+36.75`

The vertex of the parabola is `(3.5, 36.75)`