anonymous
  • anonymous
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)
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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schrodinger
  • schrodinger
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anonymous
  • anonymous
do you know how to plot graphs?
anonymous
  • anonymous
I need feedback to help you.
anonymous
  • anonymous
sorry had to step away. I have a hard time with graphing.

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anonymous
  • anonymous
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.
anonymous
  • anonymous
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.
anonymous
  • anonymous
you said the x and y both represent the independent.
anonymous
  • anonymous
sorry, y represents the dependent variable.
anonymous
  • anonymous
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.
anonymous
  • anonymous
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
anonymous
  • anonymous
then your equation would be bonus = sales/10-M-1/2tax
anonymous
  • anonymous
anyway, the point is, there are independent variables which are in your hand.
anonymous
  • anonymous
and there are other variables which depend on your independent variable.
anonymous
  • anonymous
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)
anonymous
  • anonymous
so then, what is the dependent variable, in terms of x?
anonymous
  • anonymous
Okay.
anonymous
  • anonymous
5y?
anonymous
  • anonymous
if bonus is 10% of sales, express bonus in terms of sales. similarly if 7x-5y is 15, express y in terms of x.
anonymous
  • anonymous
basically, you are trying to express the dependent variable as a function of the independent variable.
anonymous
  • anonymous
you could say that 7x-5y = 15 is " 7 times your sales minus 5 times your bonus always gives 15 grand"
anonymous
  • anonymous
so express bonus in english, or in an equation.
anonymous
  • anonymous
are you getting what I am saying?
anonymous
  • anonymous
ah not really
anonymous
  • anonymous
sorry that is one area I just seem can' get a grasp on
anonymous
  • anonymous
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
anonymous
  • anonymous
so choose your x values and find out the corresponding y values.
anonymous
  • anonymous
since this is the equation for a line, you need only two points.
anonymous
  • anonymous
ok so here is what I did. tell me if I am rght
anonymous
  • anonymous
I chose 2 for x. y=7(2)-15/5.... y=14-15/5.... y=-1/5
anonymous
  • anonymous
so how did I do?
anonymous
  • anonymous
okay thats great!
anonymous
  • anonymous
but 1/5 is kinda hard to plot on a graph.
anonymous
  • anonymous
yes very true. do I need to choose a different number or x?
anonymous
  • anonymous
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.
anonymous
  • anonymous
y is value/5.
anonymous
  • anonymous
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.
anonymous
  • anonymous
so one value could be (5,4)
anonymous
  • anonymous
ok I changed the value of x to 5. I came up with y= -3
anonymous
  • anonymous
both are nice round numbers, easy to plot on a pice of graph paper.
anonymous
  • anonymous
how did you come up with y = -3 for x = 5?
anonymous
  • anonymous
sorry fiured wrong. redid it and got 4.
anonymous
  • anonymous
okay, next choose x =10
anonymous
  • anonymous
ok I got 11
anonymous
  • anonymous
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.
anonymous
  • anonymous
right
anonymous
  • anonymous
so what is the second equation?
anonymous
  • anonymous
7x=5y+15
anonymous
  • anonymous
this is the same equation as before.
anonymous
  • anonymous
the other one was 7x-5y=15
anonymous
  • anonymous
okay, subtract 5y from both sides of your second equation and post what you got.
anonymous
  • anonymous
y=-7x+15
anonymous
  • anonymous
what?
anonymous
  • anonymous
how did you get that? http://www.dabbleboard.com/draw?b=Guest644716&i=0&c=3327a9e1158d904a38fbad735c24ed28cad7bcd9 show me there.

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