Question

Identify the vertex for the graph of y = −2x^2 + 8x − 1.

Answer 1

the vertex of the graph y = ax^2 + bx + c
is given by
x-vertex = -b/2a
as you found the x-vertex you just plug it into your equation and find y-vertex

in our case
a= -2
b = 8
c = -1

so what is
-b/2a
?

Answer 2

.5 ?

Answer 3

if b = 8 and a = -2
it means that 2a = -4

so
-(b/2a) = - (8/-4) = 2

Answer 4

this is x-vertex.. now in order to find the y-vertex
you only have to plug 2 into the equation
so what is y(2) ?

Answer 5

are you there ? trying ?

Answer 6

Yes, one sec.

Answer 7

ok good

Answer 8

It would be b because when you work it out it cannot be c.

Answer 9

yes.. this is the right answer (b)

y(2) = -2* (2)^2 +8*2 -1 = -8 + 16 -1 = 7

so (2,7)

Answer 10

Yay ! thanks

Answer 11

yw :)