Question

y=2x^2 +8x write in vertex form

Answer 1

Completing the square of 2x^2+8x will give you vertex form

Answer 2

i tried that and i got a positive b when its negative how do we fix this?

Answer 3

Show me how you completed the square

Answer 4

y=(x+2)^2-8

Answer 5

thats what i got

Answer 6

That is correct.

Answer 7

but is y= (x-2)^2 -8

Answer 8

Nope the first one was right

Answer 9

okay how about y=x^2-12x-3 how do we get this one?

Answer 10

i got y=(x+6)^2 -39 when the answer is y=(x-6)^2 -39

Answer 11

x^2-12x-3 (-12/2)^2=36

add and subtract 36

x^2-12x+36-36-3
factor first 3 terms
(x-6)^2-39

Answer 12

as a rule of thumb if the b value is negative then the h value is also going to be negative aswell right?

Answer 13

What is b and what is h?

Answer 14

-12 is b and h is -6

Answer 15

Remember how you divide the middle term by 2 and then square it to get the number that you add and subtract? The number you get before squaring will be the number you use. -12/2=-6
and so it factored (x-6)^2

Answer 16

so to get the h value we basically divide the b value by 2

Answer 17

Yep

Answer 18

alright thanks