Question

I have to find the vertex of: y= -3x^2+12x-8 and I have to plot it on a graph, providing an ordered pair as the vertex. I'm not understanding this at all. How should I begin?

Answer 1

Hoot! You just asked your first question! Hang tight while I find people to answer it for you. You can thank people who give you good answers by clicking the 'Good Answer' button on the right!

Answer 2

complete the sqaure

Answer 3

first factor out x^2 coeffiecnet

Answer 4

y = -3 ( x^2 -4x ) -8

Answer 5

note, we only factored out common factors on the x terms

Answer 6

then complete the sqaure in side the brackets

Answer 7

ok, it kinda makes sense so far..

Answer 8

to complete the square on x^2 -4x , we need to half the -4 ( to get -2 ) , the square it , and add and subtract inside the brackets

Answer 9

so y= -3 ( x^2 -4x + 4 - 4 ) - 8 // notice, its important you add and substract INSIDE THE BRACKET

Answer 10

we need to maintain equality

Answer 11

alright, with you on that

Answer 12

now you group the perfect sqaure inside the bracket

Answer 13

so y= -3 ( (x-2)^2 -4) -8

Answer 14

now you expand the brackets , being careful with the signs

Answer 15

so y= -3(x-2)^2 +12 -8

Answer 16

So I'm seeing here the only way the vertex can be solved is by doing the equation, then plotting it on the graph- how would I plot this #1, and #2, how would I come up with a solution set??

Answer 17

y= -3(x-2)^2 +4

Answer 18

vertex = (2,4)

Answer 19

you could do it other ways , you might the equation of axis of symmetry of a parabola is x=-b/2a

Answer 20

And how to plot? I have to do it on an online graph. Totally confused with it

Answer 21

and you know the vertex is on the axis of symmetry

Answer 22

I dont know there, I know how to do a general plot but have idea how the computer with mark you

Answer 23

"graph the equation by hand; find the vertex and round approximate coordinates to the second decimal place."

Answer 24

"Use the graphing tool to graph the parabola"

Answer 25

THIS is what is confusing me. Do I graph the solution set, I'm just not getting it. I understand for the most part the equation, but not plotting

Answer 26

One more equation- (x+8)^2+8(x+7)=64. I can solve by the method of my choice

Answer 27

Its not a negative sign in front of the x, I just need a solution set