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MightySmurf

  • 4 years ago

Solve this system of equations using the addition method. 3x-y=9 2x+y=6 Solve this system of equations using the addition method. 3x-y=9 2x+y=6 @Mathematics

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  1. conheomap
    • 4 years ago
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    5x + 0 = 15 x = 3 plug to the first equation 2.3 + y = 6 y = 0

  2. MightySmurf
    • 4 years ago
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    so i would just add the numbers then divide

  3. conheomap
    • 4 years ago
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    first add the equation 1 and 2 so that it will get rid of one of the variable In this example, you got it easy because in equation 1 you have -y, and in equation 2 you have y, so the sum of these equations will get rid of y

  4. conheomap
    • 4 years ago
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    in case you want to get rid of x first. then you would have to do the following: multiply 1st equation by 2 multiply 2nd equation by -3 so that it would appear like this 6x .... -6x ------------- 0x ......

  5. MightySmurf
    • 4 years ago
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    im sorry im very confused..see im takin algebra online and dnt have a teacher so i have to take tests online and have no idea how to do them

  6. conheomap
    • 4 years ago
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    ok so you have two equations and two variables which is x, y. They ask you to find those values of x, y so that when you plug them in to any equation, they have to be true. In this case if you plug x = 0 and y = 3. Both equations hold. That's how it goes anyways.

  7. conheomap
    • 4 years ago
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    Now they asked you to use addition method which means. some how you have to add equation 1 and equation 2

  8. conheomap
    • 4 years ago
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    3x-y=9 + 2x+y=6 ---------- 5x + 0 = 15 the new equation only has x now. So you know what x is, just plug into any of the equations they gave you, you will get y value.

  9. conheomap
    • 4 years ago
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    give me another problem, i'll explain in more details because this is problem is very simple.

  10. MightySmurf
    • 4 years ago
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    ok 4a-5b=7 4a+5b=17

  11. conheomap
    • 4 years ago
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    alright. this is also simple. Let's change to 4a + 5b = 7 2a + 3b = 9 instead.

  12. conheomap
    • 4 years ago
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    now what do you do? I want to know how you do it, then I'll explain

  13. MightySmurf
    • 4 years ago
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    i add 4a to 2a right

  14. conheomap
    • 4 years ago
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    continue

  15. MightySmurf
    • 4 years ago
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    then i add5b and3b

  16. conheomap
    • 4 years ago
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    ok. but the new equation doesn't get rid of any variables right? so your stuck

  17. conheomap
    • 4 years ago
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    you have to modify the original equations somehow so when adding you will get either 0x or 0y

  18. conheomap
    • 4 years ago
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    look at this problem you gave me: 4a-5b=7 4a+5b=17 notice the -5b (1st) and 5b (2nd equation). when adding the result is 0b. that's why i said they gave you a simple problem. Just adding.

  19. conheomap
    • 4 years ago
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    did you learn how to modify the equations yet? or just purely adding stuff?

  20. MightySmurf
    • 4 years ago
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    no did learn to modify the equations

  21. conheomap
    • 4 years ago
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    okay then please try to modify this one: 4a + 5b = 7 2a + 3b = 9

  22. MightySmurf
    • 4 years ago
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    i cnt i dnt understand how to modify im sorry

  23. conheomap
    • 4 years ago
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    let's try to modify so when adding I will get 0a ok?

  24. conheomap
    • 4 years ago
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    i see first equation have 4a. the 2nd have 2a. ... I need to have some how to have 2nd equation to have -4a. Right?

  25. MightySmurf
    • 4 years ago
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    ummm yes

  26. conheomap
    • 4 years ago
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    you can do this by multiply 2nd equation by -2

  27. conheomap
    • 4 years ago
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    what's the modified equation now?

  28. conheomap
    • 4 years ago
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    ok the modified (2nd equation) becomes: -4a -6b = -18

  29. conheomap
    • 4 years ago
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    now you can add the first and the modified.

  30. MightySmurf
    • 4 years ago
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    so then id add the 4a and 5b

  31. conheomap
    • 4 years ago
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    no no. it's gonna be like this: 4a + 5b = 7 + -4a -6b = -18 ----------------------- 0a -b = -11

  32. conheomap
    • 4 years ago
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    you only add the a and a... b and b not a and b.

  33. MightySmurf
    • 4 years ago
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    o

  34. conheomap
    • 4 years ago
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    so now you can solve for the b value. Once you have one variable solved, plug to any of the original equation, then bam. That's it

  35. conheomap
    • 4 years ago
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    can you modify to get rid of b instead of a this time? it's a bit harder, but same method. 4a + 5b = 7 2a + 3b = 9

  36. conheomap
    • 4 years ago
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    you have to modify both equations for b.

  37. MightySmurf
    • 4 years ago
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    4a+2a right

  38. conheomap
    • 4 years ago
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    yes what about b

  39. MightySmurf
    • 4 years ago
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    5b+3b?

  40. conheomap
    • 4 years ago
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    so you will get 6a + 8b = 16?

  41. conheomap
    • 4 years ago
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    it doesn't get rid of b does it?

  42. MightySmurf
    • 4 years ago
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    so i subtract

  43. conheomap
    • 4 years ago
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    you need to get help from professor about this. But those problems you gave me. you can just add them directly without modifying anything.

  44. conheomap
    • 4 years ago
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    you are not clear about the concept of adding.

  45. conheomap
    • 4 years ago
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    one thing I can tell you that when adding you must get rid of one of the variables.

  46. MightySmurf
    • 4 years ago
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    no im not im sorry thnks for tryin to help tho

  47. conheomap
    • 4 years ago
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    i have to go home. sorry

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