Spartan_Of_Ares
Determine whether the graph of y = x^2 + 2x − 8 has a maximum or minimum point, then find the maximum or minimum value
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Spartan_Of_Ares
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@zaynahf can you please help me?
zaynahf
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Just a minute, im getting my notes
zaynahf
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Ok do you know which way the parabola is going? Up or down?
Spartan_Of_Ares
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i think up because the x^2 is positive
Spartan_Of_Ares
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yeah it opens up
zaynahf
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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|
zaynahf
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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.
Spartan_Of_Ares
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how do i put it in vertex form?
zaynahf
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I'll give you an example one, if you dont mind
Spartan_Of_Ares
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thats fine
zaynahf
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|dw:1357600335929:dw||dw:1357600792411:dw|
Spartan_Of_Ares
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oh that make sense they dont teach that in virtual school
zaynahf
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I have a link if you want it
Spartan_Of_Ares
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OK
Spartan_Of_Ares
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would the vertex be (-0.33,-10.33)?
zaynahf
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No o.o
zaynahf
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How did you get that?
Spartan_Of_Ares
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-1,-9 if i round?
Spartan_Of_Ares
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tried the formula by plugging in the numbers
zaynahf
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Yep, its -1,-9
Spartan_Of_Ares
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wait this ask for the minimum value not the vertex
zaynahf
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So if thats the vertex, then what would be the minimum?
Spartan_Of_Ares
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im lost i may have made terrible mistakes
zaynahf
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Ok, where are you lost from?
Spartan_Of_Ares
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everything my brain just committed suicied i made mistakes a the beging all the way to the end
zaynahf
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for finding the vertex?
Spartan_Of_Ares
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i... thats what i tried but i messed up completely i didnt even simplify right
zaynahf
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where did youget up to?
Spartan_Of_Ares
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i failed at even isolating the x terms( i've been up since 3 am) :-(
zaynahf
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Isolate:
(x^2 +2x )-8
Spartan_Of_Ares
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ill be on later i have to go eat dinner
zaynahf
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ok