Question

How do you write `y=-5x^2 +x +1` in vertex form and identify the vertex, y intercept and x intercept?

Answer 1

x of vertex: `x = (-b/2a) = (-1)/-10 = 1/10`

y of vertex: `y = f(1/10) = (-5/100) + 1/10 + 1 = 105/100`

Vertex form: `f(x) = -5(x - 1/10)^2 + 105/100.`

Check by developing:

`f(x) = -5(x^2 - (2x)/10 + 1/100) -+ 105/100`
`= -5x^2 + x - 5/100 + 105/100 = -5x^2 + x + 1.` OK