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anonymous

  • 5 years ago

Hi all. I have 4 problems that I am having a very hard time with so need some help please. Solve the system of equations by graphing: 7x-5y=15 & 7x=5y+15. Need solution set (ordered pair)

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  1. anonymous
    • 5 years ago
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    do you know how to plot graphs?

  2. anonymous
    • 5 years ago
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    I need feedback to help you.

  3. anonymous
    • 5 years ago
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    sorry had to step away. I have a hard time with graphing.

  4. anonymous
    • 5 years ago
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    okay. graphs have a dependent variable and an independent variable. The x axis represents the independent variable and the y axis represents the independent variable.

  5. anonymous
    • 5 years ago
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    so, now choose any values of x for your equation 7x - 5y = 15. That is, choose any values of x and you will get a corresponding dependent value of y.

  6. anonymous
    • 5 years ago
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    you said the x and y both represent the independent.

  7. anonymous
    • 5 years ago
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    sorry, y represents the dependent variable.

  8. anonymous
    • 5 years ago
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    let me give you an example. suppose you are a salesman. Your year end bonus is 10% of sales you make that year. So, the sales you make is an independent variable. You can make 10000 dollars worth of sales, or if you are better than average, you make 20000 dollars of sales. Or if you are brilliant, you make $100,000 of sales. But notice what happens. The bonus is 10% of your sales. So the more sales you make, the more bonus you get. In other words, the bonus is dependent on sales.

  9. anonymous
    • 5 years ago
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    unfortunately all dependent variables are not so easily represented as 10% of the independent variables. suppose your bonus was 10% of sales - medicare - 1/2taxes

  10. anonymous
    • 5 years ago
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    then your equation would be bonus = sales/10-M-1/2tax

  11. anonymous
    • 5 years ago
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    anyway, the point is, there are independent variables which are in your hand.

  12. anonymous
    • 5 years ago
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    and there are other variables which depend on your independent variable.

  13. anonymous
    • 5 years ago
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    so in your equation, 7x - 5y = 15, let say x is the independent variable, just because it is nice to have the x variable on the independent axis (x-axis)

  14. anonymous
    • 5 years ago
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    so then, what is the dependent variable, in terms of x?

  15. anonymous
    • 5 years ago
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    Okay.

  16. anonymous
    • 5 years ago
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    5y?

  17. anonymous
    • 5 years ago
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    if bonus is 10% of sales, express bonus in terms of sales. similarly if 7x-5y is 15, express y in terms of x.

  18. anonymous
    • 5 years ago
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    basically, you are trying to express the dependent variable as a function of the independent variable.

  19. anonymous
    • 5 years ago
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    you could say that 7x-5y = 15 is " 7 times your sales minus 5 times your bonus always gives 15 grand"

  20. anonymous
    • 5 years ago
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    so express bonus in english, or in an equation.

  21. anonymous
    • 5 years ago
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    are you getting what I am saying?

  22. anonymous
    • 5 years ago
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    ah not really

  23. anonymous
    • 5 years ago
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    sorry that is one area I just seem can' get a grasp on

  24. anonymous
    • 5 years ago
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    okay if 7 times sales minus 5 times bonus is always 15 grand, then 7 times sales minus 15 grand divided by 5 is the bonus. in other words, y = (7x-15)/5

  25. anonymous
    • 5 years ago
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    so choose your x values and find out the corresponding y values.

  26. anonymous
    • 5 years ago
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    since this is the equation for a line, you need only two points.

  27. anonymous
    • 5 years ago
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    ok so here is what I did. tell me if I am rght

  28. anonymous
    • 5 years ago
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    I chose 2 for x. y=7(2)-15/5.... y=14-15/5.... y=-1/5

  29. anonymous
    • 5 years ago
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    so how did I do?

  30. anonymous
    • 5 years ago
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    okay thats great!

  31. anonymous
    • 5 years ago
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    but 1/5 is kinda hard to plot on a graph.

  32. anonymous
    • 5 years ago
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    yes very true. do I need to choose a different number or x?

  33. anonymous
    • 5 years ago
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    notice that y i some value/5. so if the value is a multiple of 5, then you would get a nice round number for y.

  34. anonymous
    • 5 years ago
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    y is value/5.

  35. anonymous
    • 5 years ago
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    so suppose you chose x = 5. 7 times 5 is 35, and 35-15 is 20. 20 is a multiple of 5. so y =4.

  36. anonymous
    • 5 years ago
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    so one value could be (5,4)

  37. anonymous
    • 5 years ago
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    ok I changed the value of x to 5. I came up with y= -3

  38. anonymous
    • 5 years ago
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    both are nice round numbers, easy to plot on a pice of graph paper.

  39. anonymous
    • 5 years ago
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    how did you come up with y = -3 for x = 5?

  40. anonymous
    • 5 years ago
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    sorry fiured wrong. redid it and got 4.

  41. anonymous
    • 5 years ago
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    okay, next choose x =10

  42. anonymous
    • 5 years ago
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    ok I got 11

  43. anonymous
    • 5 years ago
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    okay great! so you have two points (5,4) and (10,11). there is only one line which passes through both points. So you have your first line down on the graph! huzzah! one down, one equation to go.

  44. anonymous
    • 5 years ago
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    right

  45. anonymous
    • 5 years ago
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    so what is the second equation?

  46. anonymous
    • 5 years ago
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    7x=5y+15

  47. anonymous
    • 5 years ago
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    this is the same equation as before.

  48. anonymous
    • 5 years ago
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    the other one was 7x-5y=15

  49. anonymous
    • 5 years ago
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    okay, subtract 5y from both sides of your second equation and post what you got.

  50. anonymous
    • 5 years ago
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    y=-7x+15

  51. anonymous
    • 5 years ago
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    what?

  52. anonymous
    • 5 years ago
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    how did you get that? http://www.dabbleboard.com/draw?b=Guest644716&i=0&c=3327a9e1158d904a38fbad735c24ed28cad7bcd9 show me there.

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