katie2212 3 years ago Use elimination to solve the system. What is the value of x? 4x + 7y = -14 and 8x + 5y = 8

1. jim_thompson5910

Hint: Multiply everything in the first equation by -2 to go from 4x + 7y = -14 to -8x - 14y = 28

2. jim_thompson5910

So you now have the two equations -8x - 14y = 28 8x + 5y = 8

3. RyanL.

That's solving for x first and then plugging it back to get y. I thought that the OP wanted to do it from that one step.

4. jim_thompson5910

you can go a number of ways, you can multiply the top equation by 5 and the bottom equation by -7, then add

5. katie2212

im just getting more confused

6. jefferyflow123go

I believe the answer is -14.

7. katie2212

these are the options. 3.5 -1.5 8 -4

8. jefferyflow123go

Oh then i bet the answer is -5

9. jim_thompson5910

Do you see how I went from 4x + 7y = -14 to -8x - 14y = 28

10. jim_thompson5910

it's not -5

11. jim_thompson5910

12. jefferyflow123go

sorry, if you would just give her the right answer, i would be able to go on with my day. As would she

13. jim_thompson5910

I'm providing hints and trying to walk her through it (without giving it all away)

14. jefferyflow123go

No matter how many hints your provide she doesn't care. she just wants the answer

15. jim_thompson5910

well that's not what this site is for, I'm sry

16. jim_thompson5910

if you keep this behavior up jefferyflow123go you will be reported (and possibly suspended/banned)

17. katie2212

its hard for me too understand..im trying. i learn better in a class room thats why i am having trouble with my online class

18. jim_thompson5910

its ok, you don't have to understand everything at once katie2212

19. katie2212

but i have to understand if i want to finishe this exam.

20. jefferyflow123go

Sorry for hekping. My mom always taught me to hekp and have pride in my work, so trying to be of assistance. I didn;t realize that you can be the only genious here. If you were that smart you'd know that she doesn't understand your hints and just wants the answer.

21. jim_thompson5910

that's not helping though, you may think it is...but it's not

22. jim_thompson5910

if you want, you can provide the steps so she can learn from them

23. katie2212

okay will you guys please stop arguing and just help me!

24. jim_thompson5910

ok I'll give steps on this one and hopefully it will be enough to answer similar ones, sound good?

25. jefferyflow123go

IS your refrigderator running ? IF SO GO CATCH IT

26. katie2212

yes thank you

27. jefferyflow123go

My momma once told me, a fast runna' is the best runnna'

28. katie2212

jeffery if youre not going to help please get out.

29. jefferyflow123go

30. jefferyflow123go

What did the bison say to his son when he left for college? Bi-son

31. jim_thompson5910

4x + 7y = -14 ... Start with the first equation -2(4x + 7y) = -2*(-14) ... Multiply both sides by -2 -8x - 14y = 28 ... Distribute and multiply --------------------- So 4x + 7y = -14 is the same as -8x - 14y = 28 --------------------- This means that the system 4x + 7y = -14 8x + 5y = 8 becomes -8x - 14y = 28 8x + 5y = 8 Now add the two equations: -8x - 14y = 28 8x + 5y = 8 -------------- 0x - 9y = 36 which means that -9y = 36 Solve for y to get -9y = 36 y = 36/(-9) y = -4 Now that we know that y = -4, we can use this to find x. Pick on any equation, plug in y = -4 and solve for x 4x + 7y = -14 4x + 7(-4) = -14 4x - 28 = -14 4x = -14 + 28 4x = 14 x = 14/4 x = 7/2 x = 3.5 So the value of x is x = 3.5

32. jefferyflow123go

IM SO PUN-NY

33. jefferyflow123go

IM A MaTH WIZ

34. katie2212

Thank you Jim

35. jefferyflow123go

yanno wizard like Harry Potter

36. jim_thompson5910

The idea here is to get the x coefficients equal and opposite. Then you add the equations. Doing so will cancel out the x terms so you can solve for y

37. jim_thompson5910

then you use that value of y to find x

38. jim_thompson5910

you've been reported jefferyflow123go, have a nice day

39. jefferyflow123go

you too good sir(:

40. jim_thompson5910

good luck with that one, I don't spam and harass others so your claim will be without merit