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EmmaH

  • 2 years ago

PLEASE HELP!!!! Solve the system, using substitution. One point for correct steps, one point for correct ordered pair, (a,b). a + b = 4 and 2a + 3b = 11 i tried to solve for a but ended up with 1/-5 i dont think thats right....

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  1. ayushprasad
    • 2 years ago
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    |dw:1356562594798:dw|

  2. seidi.yamauti
    • 2 years ago
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    a+b=4 2a+3b=11 a=4-b 2(4-b)+3b=11 (substituing a as found) a=4-b 8+b=11 a=4-b b=3 so, a=1 and b=3

  3. EmmaH
    • 2 years ago
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    a=4-b 2(4-b)+3b=11 i get that but how did ypu go from that to a=4-b 8+b=11

  4. seidi.yamauti
    • 2 years ago
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    you need first to isolate a or b in one of the equations, and use this on the other. I have skipped one or two steps, but if you do correctly, the answer (a,b)=(1,3) will be found

  5. seidi.yamauti
    • 2 years ago
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    2(4-b) = 8-2b, write it and keep solving

  6. seidi.yamauti
    • 2 years ago
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    This problem is about solving what is called 'linear system'. You have some equations with letters and need to find what are their values. Further you will see that not all of this kind of systems can be solved (when there are more letters than equations) - but you can just ignore it by now tell me when you're done, it just a matter of practice to solve it better an faster

  7. EmmaH
    • 2 years ago
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    ok question: in 2(4-b)+3b=11 would it equal 8-b+3b=11 or 8-2b+3b=11?

  8. seidi.yamauti
    • 2 years ago
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    8-2b+3b=11

  9. seidi.yamauti
    • 2 years ago
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    because the 2 multipies both 4 and -b in 2(4-b)

  10. EmmaH
    • 2 years ago
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    this is what i got 8-b+3b=11 8+2b=11 2b=11-8 2b=3 2b/2=3/2

  11. seidi.yamauti
    • 2 years ago
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    re-do it haha it is 8-2b+3b=11 but what you've done is right if it was 8-b+3b=11

  12. taylorstenger
    • 2 years ago
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    |dw:1356564451980:dw|

  13. seidi.yamauti
    • 2 years ago
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    kind of what taylor said... You need to do all by yourself, and just ask for some tips. Because it is when you think alone that you really understand. try and try and try. It's hard, but sometime there will be just the right answer

  14. taylorstenger
    • 2 years ago
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    Yup. U cant just go on the internet and find answers for everything and anything. Theres a reason its in ur text books, and theres a reason teachers teach it to u. If u paid attention, u wouldnt be askin questions on OpenStudy ;-)

  15. EmmaH
    • 2 years ago
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    im not trying to gte an easy answer i honestly dont understand this also i didnt respond bcs my inter net went out

  16. seidi.yamauti
    • 2 years ago
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    I was just complementing. Just to say, first step, you can ask a lot about your doubt, but with time, you will do it without any help. haha

  17. EmmaH
    • 2 years ago
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    im really confused about what to do after i get -2b=3 can you please continue to help me?

  18. seidi.yamauti
    • 2 years ago
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    i'm here. Let's see..

  19. seidi.yamauti
    • 2 years ago
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    where is -2b=3 ?

  20. EmmaH
    • 2 years ago
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    8-2b=11 -2b=11-8 -2b=3

  21. seidi.yamauti
    • 2 years ago
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    you have a+b=4 2a+3b=11 then, you use ANY of these equations to isolate a letter in the case, I've used the first and came up with a=4-b (so, from now on, that's what a is) you could also do it in the second, but that's too much work

  22. seidi.yamauti
    • 2 years ago
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    I isolated a, but it could be also b. both correct

  23. EmmaH
    • 2 years ago
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    thisd is what ive done a + b = 4 and 2a + 3b = 11 2(4-b)+3b=11 8-b+3b=11 8-2b=11 -2b=11-8 -2b=3

  24. EmmaH
    • 2 years ago
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    what next?

  25. seidi.yamauti
    • 2 years ago
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    2(4-b)+3b=11 8-b+3b=11 This is not right, because when you multiply a number times something in parenthesis, everything inside is multiplied so 2(4-b)+3b=11 what comes next?

  26. EmmaH
    • 2 years ago
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    8-2b+3b=11?

  27. seidi.yamauti
    • 2 years ago
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    yes!

  28. seidi.yamauti
    • 2 years ago
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    and i guess, if you go back to my first post, it will make more sense now

  29. EmmaH
    • 2 years ago
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    8-1b=11 -1b=11-8 -1b=3 -1b/-1=3/-1 b=-3 is that right

  30. seidi.yamauti
    • 2 years ago
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    nonononoooo you've got 8-2b+3b=11 which is equal to 8+b=11 not 8-b=11

  31. EmmaH
    • 2 years ago
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    8+b=11 b=3 ??

  32. seidi.yamauti
    • 2 years ago
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    YES! hahahaha

  33. EmmaH
    • 2 years ago
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    XD

  34. EmmaH
    • 2 years ago
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    (1,3) ?

  35. seidi.yamauti
    • 2 years ago
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    That's it :)

  36. EmmaH
    • 2 years ago
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    thank you for taking the time to help me!

  37. seidi.yamauti
    • 2 years ago
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    i've found the khan academy page on algebra. https://www.khanacademy.org/math/algebra This may help you

  38. seidi.yamauti
    • 2 years ago
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    and you're welcome

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