Question

Does anyone know how to find the maximum value for y=-2x^2+8x-5?

Answer 1

You need to find the vertex. Do you know how to do this?

Answer 2

yes

Answer 3

What do you get for the vertex?

Answer 4

-b/2a

Answer 5

in this case,

a = -2
b = 8

Answer 6

I mean 2

Answer 7

sorry, my bad

Answer 8

So what is the x coordinate of the vertex?

Answer 9

I"m not sure

Answer 10

Plug in a = -2 and b = 8

Answer 11

wait into -b/2a?

Answer 12

Yes, into -b/(2a)

Answer 13

x = -b/(2a)

Answer 14

oh, I did I received 2 ( I mentioned in the earlier comments)

Answer 15

x=2

Answer 16

good, that's the x coordinate of the vertex

Answer 17

Plug that x value into y=-2x^2+8x-5 to get the y coordinate of the vertex

Answer 18

wait is that all?

Answer 19

but isn't that how u find the minimum?

Answer 20

That's if a > 0

In this case, a < 0

Answer 21

If a > 0, then y = ax^2 + bx + c will have a minimum

If a < 0, then y = ax^2 + bx + c will have a maximum

Answer 22

ohh, so technically finding the minimum and maximum can be solved by the same way?

Answer 23

well, ok thank-you I understand it now

Answer 24

Yes they are solved the exact same way. The only difference will depend on the value of 'a' as shown above.

Answer 25

ohhhhhhhhhhhhhh, ok thank-you again

Answer 26

yw