Question

what is the vertex of y= -2x2 + x +1

Answer 1

Remember how you found b earlier?

Answer 2

foil?

Answer 3

Here, a=-2, b=1, c=1

Answer 4

Yes, but you don't have to foil here, just recognize a,b,c

Answer 5

The vertex of a parabola written in this form ax^2+bx+c is the point
\[(\frac{-b}{2a},f(\frac{-b}{2a}))\]

Answer 6

So you can find the x-coordinate by evaluation -b/(2a)

Answer 7

so 1/a(-2)

Answer 8

1/2(-2)

Answer 9

remember the negative sign

Answer 10

for b

Answer 11

-b/(2a)=-1/(2*(-2))

Answer 12

ohh okay

Answer 13

but you're not done yet

Answer 14

you have the x-coordinate, which is 1/4, what is the y-coordinate?

Answer 15

to get the y-coordinate plug in (1/4) for x in the equation

Answer 16

okay