Determine whether the graph of y = x^2 + 2x − 8 has a maximum or minimum point, then find the maximum or minimum value

- anonymous

- jamiebookeater

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- anonymous

@zaynahf can you please help me?

- anonymous

Just a minute, im getting my notes

- anonymous

Ok do you know which way the parabola is going? Up or down?

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- anonymous

i think up because the x^2 is positive

- anonymous

yeah it opens up

- anonymous

Right! So based on that, it tells you whether your vertex will have a maximum or minimum value. When it is opening up (a value is +), there will be a minimum because the vertex is on the bottom, the lowest point of the parabola. When it is opening down (a value is -), there will be a maximum value because the vertex is at the top, the highest point of the parabola. When naming the min/max, you only use the y value of the vertex.
Example:|dw:1357599979562:dw|

- anonymous

One more thing: IF you know how to find a vertex when it is in standard form, you can do that, but personally i find it easier to first complete the square (make it into vertex form). If you need to know how to do either, let me know.

- anonymous

how do i put it in vertex form?

- anonymous

I'll give you an example one, if you dont mind

- anonymous

thats fine

##### 1 Attachment

- anonymous

|dw:1357600335929:dw||dw:1357600792411:dw|

- anonymous

oh that make sense they dont teach that in virtual school

- anonymous

I have a link if you want it

- anonymous

OK

- anonymous

http://www.youtube.com/watch?v=aDHq_FoRxZQ
Explains it better than i did

- anonymous

would the vertex be (-0.33,-10.33)?

- anonymous

No o.o

- anonymous

How did you get that?

- anonymous

-1,-9 if i round?

- anonymous

tried the formula by plugging in the numbers

- anonymous

Yep, its -1,-9

- anonymous

wait this ask for the minimum value not the vertex

- anonymous

So if thats the vertex, then what would be the minimum?

- anonymous

im lost i may have made terrible mistakes

- anonymous

Ok, where are you lost from?

- anonymous

everything my brain just committed suicied i made mistakes a the beging all the way to the end

- anonymous

for finding the vertex?

- anonymous

i... thats what i tried but i messed up completely i didnt even simplify right

- anonymous

where did youget up to?

- anonymous

i failed at even isolating the x terms( i've been up since 3 am) :-(

- anonymous

Isolate:
(x^2 +2x )-8

- anonymous

ill be on later i have to go eat dinner

- anonymous

ok

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