Ask a Question

what is x and y in this equation

0 votes

      

              7x+9y-28

    

         

asked Mar 1, 2014 in Mathematics by anonymous
   

1 Answer

+5 votes
You did not post an equation. An equation must include an equals sign. Did you mean to post 7x + 9y = 28?

I am going to write an answer assuming you meant 7x + 9y = 28.

Without a second independent equation that uses one or both of these variables, you cannot solve for a single set of values. But you can solve for all values of x with respect to y or all values of y with respect to x.

7x + 9y = 28 (subtract 9y from both sides of the equation)

7x = -9y + 28 (divide both sides of the equation by 7)

x = -(9/7)y + 4

You now have a solution set for all values of x with respect to y

(x, -(9/7)y + 4)

You can select values for y and solve for x to have a definite solution set, but there is an infinite number of solution sets. Example:

Let y = 7/9

x = -(9/7)(7/9) + 4 = -1 + 4 = 3

So (3, 7/9) is a solution set. Try these two numbers in the original equation.

7(3) + 9(7/9) = 28

21 + 7 = 28

This equation is true, so (3, 7/9) is a solution set.

You can illustrate all solution sets with a linear graph by solving for y with respect to x.

7x + 9y = 28 (subtract 7x from both sides of the equation then divide both sides by 9)

y = (-7/9)x + 28/9

This is the y-intercept form of a linear equation. Its slope is -7/9 and its y-intercept is 28/9. A graph of the line illustrates all solutions for the given equation.
answered Mar 2, 2014 by stg1.stewart Inquisitive Expert (21,460 points)

Categories

ExplainPlease on Facebook

75,014 questions

48,872 answers

1,169 comments

82,583 users

CuriousGirl313,480
BobTheAnswerGuy310,070
smartguy111,120
charlie100,740
bbrown97,580
answerwiz94,860
The.Sage93,460
amanda0192,460
kfox83,500
lsmith82,840
...