SOLUTION: hello! i need help getting the vertex form of y=-3x^2+12x-8. I have a test tommarow and i dont get it:(

Question 744398: hello! i need help getting the vertex form of y=-3x^2+12x-8. I have a test tommarow and i dont get it:(
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
The vertex form of the equation of a parabola is
with a coefficient and using the coordinates (h,k) of the vertex.

A SLOW AND EASY WAY:
If you expand the square in you get
-->
If you compare that to you realize that:
the coefficient of is , and
the coefficient of is
That gives you the values of and :
was clear, and substituting that value in you get
--> --> -->
Plugging those values into
you get
--> --> -->
Comparing that last equation to , you realize that the independent term (the part without any ) is
--> -->
Plugging the values found for , , and into you get
.

THE FAST AND STEEP WAY that makes you look so smart:
--> (taking out (-3) as common factor from
--> (adding and which cancel out)
--> --> --> .

THE MEMORIZED FORMULA WAY:
-->
For , , and so
and
so
the vertex form is .

NOTE:
If your teacher favors the fast and steep way, show your teacher that way (even if you figured it out a different way on a separate piece of paper).
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