A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • 5 years ago

So, I got this problem right but I did it different from the teacher. I just plugged in numbers. How do I solve this easier than that? -x+3y=10 4x+y=25 Solve for x and y

  • This Question is Closed
  1. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i take it this is a system of equation?

  2. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the 2nd equation is easier to "solve for y"

  3. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    when you have "y" in terms of "x", you can use it in the 1st equation in the place of "y"... does that make sense?

  4. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    y = -4x + 25 (from teh second equation) -x + 3(-4x+25) = 10 (solve for x)

  5. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -x -12x +75 = 10 75-10 = x+12x 65 = 13x 65/13 = x .... if I did it right :)

  6. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i got x= 5/3 and y =6 1/4

  7. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    x = 5 is a solid number, so we use that in our "equation for y" to determine the value of "y" y = -4x +25 y = -4(5) +25 y = -20 + 25 y = 5 x = 5 ... i think :)

  8. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mit; whats your substitution for "y"; your y=equation?

  9. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    amistre64 that is right. I answered it right I just didn't know how to solve it without plugging in numbers

  10. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Thanks

  11. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    dian; does what I did make sense to you?

  12. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i isolate y in te second equation , then plugged tto the first eqution to solve for x

  13. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mit; what did you get for your y= equation?

  14. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Im off ; i got y= 25 /4x

  15. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mit; that would be in error work it out step by step for me please

  16. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

  17. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    4x+y=25 ... what do we do first?

  18. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    we have "addition" involved; how do we get rid of a term that is held on by "addition"?

  19. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok so yes that makes sense now. You isolated y then plugged that into the second equation to solve for x. It threw me off when I had two different letters to solve for.

  20. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    4x + y=25 4x+y/4x=25/4x, so I plug it to the first equ. -x +3(25/4x)=10

  21. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    :) yes dian

  22. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Mit: you cant divide out of an addition problem.... you have to work it out with addition/subtraction. Hint: 4x-4x = 0 and y+0=y

  23. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    4 + 6 = 10 6 does NOT equal 10/4 do you see that? 4 + 6 = 10 4-4 + 6 = 10 - 4 0 + 6 = 10 - 4 6 = 6

  24. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah I get it, so how do you solve it?

  25. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    4x+y=25 we are stuck to the "y" by addition/subtraction. So, we need to get rid of that 4x thru addition/subtraction. 4x-4x +y = 25 - 4x you see what I did there?

  26. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes

  27. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I look at it like this: if we are stuck by addition /subtraction ... we need to first get rid of the "neighbors". If anything is still stuck to the "y" it is going to be by multiplication/division... luckily, y is all by itself after we kick out the "neighbors".

  28. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so the value of "y" = 25 - 4x correct?

  29. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes sir

  30. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    good, now we "replace" this value of "y" in the other equation and solve that one for "x". -x+3(25-x)=10 How do we solve this for "x"?

  31. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i get x = 10/ 87 , that s not right is it?

  32. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i dont know, which method do we choose

  33. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    we have a few things to do first... remember what the "distributive" property tells us? we know this: 3(10) = 30 right? so, 3(6+4) should also equal 30... the distributive property says we can do this: 3 (6+4) 3(6) + 3(4) 18 + 12 = 30 ... which is what we already know right? Lets try it on this: 3(25 - x) 3(25) - 3(x) = 75 - 3x right?

  34. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -x + 75 - 3x = 10 we can add up our "x"s and kick the neighbor (75) out: -x -3x +75-75 = 10 - 75 -4x = -65 you with me so far?

  35. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah

  36. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    it would work out better if I kept track of my numbers lol... 3 (25-4x) 3(25) - 3(4x) = 75 - 12x... -x -12x +75-75 = 10 -75 -13x = -65 .... this is were we should be at :)

  37. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    when im wrong tell me :)

  38. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    LOL, i was gunna point it out

  39. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    now, we want that "x" all by itself but its got a leech, a spuse hanging on its side that we gotta get rid of.... this is a case for multiplication/division to get rid of the spouse.. -13x/13 = -65/ -13 remember that 2 negatives is a positive,,, x = 65/13. this reduces to 5 5(13) = 65 x = 5

  40. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -13x/-13 of course is what i meant lol... my keyboard hates me :)

  41. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    remember; 1st, get rid of the neighbors with addition/subtraction; 2nd, get rid of the spouse with multiplication/division... make sense?

  42. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    OK Now I got it,,

  43. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    since we have a solid nuber for x.. x=5... we use this in our "what does y equal" equation to get a solid value for "y" "y" = 25 - 4x y = 25 - 4(5) y = 25 - 20 y = 5

  44. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    we now know that y = 5 and x = 5 is the solution to this system of equations :) TADA!!!

  45. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    cool beans

  46. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    kick out the neighbors; then git rid of the spuse...... in that order! Gotta get to class now, Ciao :)

  47. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.