## iwanttogotostanford one year ago HEY NEED HELP ASAP PLEASE: Using the completing-the-square method, find the vertex of the function f(x) = –2x^2 + 12x + 5 and indicate whether it is a minimum or a maximum and at what point. Maximum at (–3, 5) Minimum at (–3, 5) Maximum at (3, 23) Minimum at (3, 23)

1. zzr0ck3r

$$f(x)=ax^2+bx+c\\f(x)=a(x+\frac{b}{2a})^2+c-\frac{b^2}{4a}$$ Has vertex $$(-\frac{b}{2a}, c-\frac{b^2}{4a})$$ This is a maximum if $$a<0$$ and a minimum if $$a>0$$

2. iwanttogotostanford

i am stuck between A and B

3. iwanttogotostanford

@zzr0ck3r

4. iwanttogotostanford

@Nnesha

5. iwanttogotostanford

@Hero

6. zzr0ck3r

Do you not understand something I wrote?

7. iwanttogotostanford

NO i am just stuck between answer A and B

8. zzr0ck3r

9. iwanttogotostanford

i just want to know if i got it right and i am stuck between A and B!

10. Hero

For quadratic functions with the form f(x) = ax^2 +bx+c , if a is negative, then the function will have a maximum value at the vertex.

11. zzr0ck3r

that is not what we are here for.

12. zzr0ck3r

@hero must be on his phone, that took way to long and your just repeating :P

13. Hero

Yeah, I don't have the best tools right now.

14. iwanttogotostanford

s o it is A?

15. Hero

.Not tellin

16. iwanttogotostanford

i did the work but I'm just stuck between minimum and maximum which is A or B! p

17. Hero

We've given you enough info.

18. iwanttogotostanford

i don't know yet.

19. iwanttogotostanford

how do i tell between minimum and maximum

20. Hero

21. iwanttogotostanford

i did i still don't know A or B

22. iwanttogotostanford

@mathway

23. Hero

This is similar to what happens when you give someone money, but they don't Know how to spend it.

24. iwanttogotostanford

who wouldn't know how to spend money

25. iwanttogotostanford

26. anonymous

Have you found the vertex form?

27. iwanttogotostanford

well kind of, i am just stuck between a and B

28. anonymous

Can you show me the steps you did?

29. iwanttogotostanford

i have it all written on paper i can't take a picture..

30. anonymous

You can select the Draw button to write your work.

31. iwanttogotostanford

well for my last step i Got A!! finally figured how to do it:-)

32. anonymous

So you will not show your work then? Okay.

33. iwanttogotostanford

no, i got the answer- thanks anyways though! @mathway

34. anonymous

All right, but I won't say if you're right or wrong.

35. iwanttogotostanford

ok

36. iwanttogotostanford

i know I'm right so thank you though