## anonymous 3 years ago how do you write y = 2x2 + 6x + 4 in general form?

1. anonymous

do u know the general form?

2. anonymous

yes, y=a(x-h)^2+k

3. anonymous

did u need it in linear form?

4. anonymous

like the general form of a linear equation?

5. anonymous

just the general form of a quadratic equation

6. anonymous

okay, so u need to know the quadratic formula i believe..do u know it?

7. anonymous

general form> y=a(x-h)^2+k

8. anonymous

oh, yeah!

9. anonymous

10. anonymous

but how does that help convert it to general form?

11. anonymous

I thought it just helped find the x-intercepts..

12. anonymous

if i can remember this correctly, i believe u need to first solve to get the values of a,b,c and then you just plug it into the general form... I'm not 100% sure tho... @abb0t, am i remembering this correctly? ;/

13. anonymous

I know how to convert it... the problem is the 2 in 2x^2

14. abb0t

General form of what?

15. anonymous

16. anonymous

2 in 2x^2 is the problem.... you isolate the x variables getting: y-4=2x^2+6x then complete the square and balance the equation: 6/2=3 3^2=9, y-4+9=2x^2+6x+9, y+5=2x^2+6x+9 then convert the trinomial into a binomial... thus lies my dilemma

17. anonymous

sorry, i'm not very sure, cuz i don't think i remember this correctly ahha and i don't wanna help u wrongly haha @Mertsj probs knows :) good luck!!! :D

18. anonymous

thanks (:

19. Mertsj

$y=2x^2+6x+4$ $y=2(x^2+3x+______ )+4$

20. Mertsj

Now complete the square by adding (3/2)^2 inside the parentheses: $y=2(x^2+3x+(\frac{3}{2})^2)+4-\frac{9}{2}$

21. Mertsj

Now factor: $y=2(x+\frac{3}{2})^2-\frac{1}{2}$

22. anonymous

why 3/2?

23. Mertsj

I want to show you something: $x^2+6x+9=(x+3)^2$

24. Mertsj

$x^2+8x+16=(x+4)^2$

25. anonymous

I don't get what you did with: (3/2^2)+4−92

26. Mertsj

Notice the relationship between the coefficient of x and the constant term in a trinomial square.

27. Mertsj

If you take 1/2 the coefficient and square it, you get the constant term.

28. Mertsj

So I took 1/2 of 3 and got 3/2. Then I squared it and added it to the x^2 + 3x to get a trinomial square.

29. Mertsj

Now the (3/2)^2 was inside a parenthesis which has a 2 in front of it so I was really adding 2 times (3/2)^2 which is 2 times 9/4 which is 9/2. So since I could not change the equation, I then had to subtract 9/2.

30. Mertsj

31. anonymous

I think so

32. anonymous

Okay, yes! I get what you did (: thank you! what were you trying to show me with those other two equations?

33. Mertsj

The relationship between the coefficient of x and the constant term.

34. anonymous

oh, that half of the coefficient of x to the second power = the constant. okay, cool

35. anonymous

Thank you for helping me (:

36. Mertsj

yw