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

1. Spartan_Of_Ares

2. zaynahf

Just a minute, im getting my notes

3. zaynahf

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

4. Spartan_Of_Ares

i think up because the x^2 is positive

5. Spartan_Of_Ares

yeah it opens up

6. zaynahf

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|

7. zaynahf

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.

8. Spartan_Of_Ares

how do i put it in vertex form?

9. zaynahf

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

10. Spartan_Of_Ares

thats fine

11. zaynahf

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

12. Spartan_Of_Ares

oh that make sense they dont teach that in virtual school

13. zaynahf

I have a link if you want it

14. Spartan_Of_Ares

OK

15. zaynahf

16. Spartan_Of_Ares

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

17. zaynahf

No o.o

18. zaynahf

How did you get that?

19. Spartan_Of_Ares

-1,-9 if i round?

20. Spartan_Of_Ares

tried the formula by plugging in the numbers

21. zaynahf

Yep, its -1,-9

22. Spartan_Of_Ares

wait this ask for the minimum value not the vertex

23. zaynahf

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

24. Spartan_Of_Ares

im lost i may have made terrible mistakes

25. zaynahf

Ok, where are you lost from?

26. Spartan_Of_Ares

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

27. zaynahf

for finding the vertex?

28. Spartan_Of_Ares

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

29. zaynahf

where did youget up to?

30. Spartan_Of_Ares

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

31. zaynahf

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

32. Spartan_Of_Ares

ill be on later i have to go eat dinner

33. zaynahf

ok