Question

How to find the vertex, domain, and range of y=-2x^2+8x-3?

Answer 1

@agent0smith

Answer 2

the domain is all real numbers, because you can use any number.

Answer 3

\[\large x = -\frac{ b }{ 2a }\]to find the x coordinate of the vertex

Answer 4

What's an x coordinate.

Answer 5

x will be 4?

Answer 6

An x coordinate is... an x coordinate.

yes, the x coordinate of the vertex is 4. Plug that into the equation for y, to find the y coordinate.

Answer 7

it's 5.

Answer 8

-2(4)^2 + 8(4) - 3 = ?

Answer 9

no i did it like this f(2)=-2(2)^2+8(2)-3.

Answer 10

why?

Answer 11

because I checked online and it told me to do that.

Answer 12

What told you to do that?

We already found x=4. The x coordinate of the vertex is 4. Plug x=4 into the equation for y, to find the y coordinate.

You plugged in x=2...

Answer 13

-2 times 2 equal =-4.

Answer 14

Plug in x=4:

y = -2(4)^2 + 8(4) - 3 = ?

Answer 15

y = 21?

Answer 16

Oh crap, i just realized that x = -b/2a = -8/(2*-2) = 2, somehow didn't notice that earlier

You're right that x=2, y=5, so the vertex is (2, 5)

Answer 17

ha I told you I'm better than you.

Answer 18

lol okay

Answer 19

I'm just kidding.