Thread: Algebra 2 help: Going from standard form to vertex form?

Hey,

I'm having trouble figuring out this one problem and I need a little help.

The question is:

What is the vertex form of the equation?
y = x^2 - 2x + 8

the choices are:
a. y = (x+1)^2 + 7
b. y = (x+1)^2 - 7
c. y = (x-1)^2 + 7

How do you figure this out?

Thanks in advance,
Brooke

Originally Posted by wakefuldoze

Hey,

I'm having trouble figuring out this one problem and I need a little help.

The question is:

What is the vertex form of the equation?
y = x^2 - 2x + 8

the choices are:
a. y = (x+1)^2 + 7
b. y = (x+1)^2 - 7
c. y = (x-1)^2 + 7

How do you figure this out?

complete the square of the given quadratic function ... or expand the given choices and combine like terms.

I did that but still got the wrong answer? Where am I going wrong?

I did this:

y = x² - 2x + 8

(-2/2)² = (-1)² = 1

= (x²- 2x + 1) + 8 + 1

= (x-1)² + 9

What did I do wrong??

Originally Posted by wakefuldoze

I did that but still got the wrong answer? Where am I going wrong?

I did this:

y = x² - 2x + 8

y = (x²- 2x + 1) + 8 - 1

...

Oh I think I got it! Is it c?

Well I am just going to go with that. Thanks for all your help.