## iwanttogotostanford one year ago NEED HELP ASAP PLEASE: Solve x^2 + 8x − 3 = 0 using the completing-the-square method. x = four plus or minus the square root of three x = negative four plus or minus the square root of three x = four plus or minus the square root of nineteen x = negative four plus or minus the square root of nineteen

1. iwanttogotostanford

@pooja195 @Nnesha

2. Jack1

complete the square is: turn this $$\large ax^2 + bx + c = 0$$ into this $$\large a(x+d)2 + e = 0$$ remember: $$\Large d = \frac b{2a}$$ $$\Large e = c - \frac{b^2}{4a}$$

3. iwanttogotostanford

so it would be C right???

4. Jack1

your equation is: $$\large x^2 + 8x + (-3) = 0$$ so turn it into this: $$\large a(x+d)2 + e = 0$$ by first solving: $$\Large d = \frac b{2a} =???$$ $$\Large e = c - \frac{b^2}{4a} = ???$$

5. iwanttogotostanford

ok, and i go C

6. Jack1

correct, C

7. iwanttogotostanford

it is really? i did it right?:-D

8. Jack1

yep

9. iwanttogotostanford

tjanks!

10. Jack1

np

11. iwanttogotostanford

could you help with one more? @Jack1

12. Jack1

wait... neg 4 negative 4! dammit, sorrt D not C

13. Jack1

*sorry ;(

14. iwanttogotostanford

aww ok:-( thanks again! can i ask you one more

15. Jack1

sure

16. iwanttogotostanford

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)

17. Jack1

ok, so have u completed the square?

18. iwanttogotostanford

yes

19. Jack1

and ur equation is now...?

20. iwanttogotostanford

2x^2+35x?

21. Jack1

no. what are a, b and c in ur original equation?

22. iwanttogotostanford

X2 8 -2

23. Jack1

no. $$\large ax^2 + bx + c = 0$$ $$\large 2x^2 + 12x + 5 = 0$$ so a is 2 b is 12 c is 5... right?

24. Jack1

u with me?

25. Jack1

r u still there?

26. iwanttogotostanford

yes! sorry what now? @jack1