## anonymous 5 years ago Use the quadratic formula to find the zeros of the function. y = 16x2 + 40x + 25 A. {-1.25, 1.25} B. {-1.25} C. {-4, 5} D. {-0.8}

1. anonymous

Quadratic formula $(-b \pm \sqrt{b^2-4ac})/2a$ where a, b, c $ax^2+bx+c=0$

2. anonymous

Can you see why you need to use the quadratic formula now?

3. anonymous

ok Go on the steps to solve it confuse me cuz there so long.

4. anonymous

so in your case, 16=a, 40=b, 25=c. Plug them into the equation that Romero showed you.

5. anonymous

You want to find the zeros of function Y right? that means y=0 first do that you get $16x^2+40x+25=0$

6. anonymous

mkay wow go on that makes so much more sense than anything my teachers are saying does

7. anonymous

like jessie said a =16 b=40 c=25 now plug them in the equation I gave you on top.

8. anonymous

ok then i will then what do i do u dont have to give me the answer i just need the simple non confusing steps ur giving me.... ^^

9. anonymous

The $\pm$means that you have to do one with + and one with - so it makes sense that you should get two values. You should be able to plug them in and whatever you get is the answer for X

10. anonymous

ok ill plug them in for you but you work it out

11. anonymous

ok i will i dont need the answer! lol just the steps!

12. anonymous

a= 16 b=40 c=25 $x= (-b \pm \sqrt{b^2-4ac})/2a$ so if I plug them in I get $x= (-40 + \sqrt{40^2-4*16*25})/(2*16)$ $x= (-40 - \sqrt{40^2-4*16*25}) / (2*16)$

13. anonymous

so just do all the multiplication division etc and you should get your answers

14. anonymous

OH!!!! Ok thank you thank you!! xD

15. anonymous

I plugged the first numbers in and then i got 8.75 as my answer... but thats not on the options!

16. anonymous

17. anonymous

i did!! thats why it took so long!

18. anonymous

Ignore the rest, and look under the radical. Start 40^2, which is 1600. Then look at the rest of what is under the radical. Do -4x16x25. Do you get -1600? So the square root of 1600-1600 is 0.

19. anonymous

Are we good to there?

20. anonymous

yea i got that

21. anonymous

but i didnt get the 1600 part for the first part i accidentally

22. anonymous

put 4 because i squared the 40 then wasnt thinking and then i got the square root which was.. 40

23. anonymous

so then would you do -40 + 32 ?

24. anonymous

wait no im confused

25. anonymous

Well remember, 2x16 is 32, but your not adding, you are dividing.

26. anonymous

So You would have -40 plus the square root of all that junk that turned out to be zero.

27. anonymous

-40/32 is -1.25

28. anonymous

29. anonymous

wow ok thx i didnt even see that!!!

30. anonymous

No. At the end, you set your equation OVER 2a. In other words, divide it by 2a.

31. anonymous

ohhhhh ok?

32. anonymous

http://www.regentsprep.org/Regents/math/algtrig/ATE3/quadsongs.htm memorize the equation, if you're in Algerbra or Algerbra 2 you're gonna use it again!

33. anonymous

algebra*

34. anonymous

ok thx!!! ya im in Algebra IIthe only reason im bad is because of all the confusing steps!!!! :P but thx u helped me ALOT!!!

35. anonymous

No problem.

36. anonymous

What a pun

37. anonymous

wait wait so i wrote the problem down like this: x = (-b + - Square root of… B^2 – 4ac /2a

38. anonymous

and then were we doing b^2 - 4ac or somethin?

39. anonymous

bc i didnt understand why i would divide by 2a again which was 32

40. anonymous

wait ok im confused UGH! i thought i got it!!!