Question

What is the vertex form of `y = x^2 − 5x − 21`?

Answer 1

`y=(x-5/2)^2-109/4`

Explanation:

`"the equation of a parabola in "color(blue)"vertex form"` is.

`color(red)(bar(ul(|color(white)(2/2)color(black)(y=a(x-h)^2+k)color(white)(2/2)|)))`

`"where "(h,k)" are the coordinates of the vertex and a"`
`"is a multiplier"`

`"to obtain this form use the method of "color(blue)"completing the square"`

`• " ensure the coefficient of the "x^2" term is 1 which it is"`

`• " add/subtract "(1/2"coefficient of x-term")^2" to"`
`x^2-5x`

`y=x^2+2(-5/2)xcolor(red)(+25/4)color(red)(-25/4)-21`

`rArry=(x-5/2)^2-109/4larrcolor(red)"in vertex form"`