Question 24119: I am graphing linear eaquations. If I have a problem like ( 2x + 7y =9 ) i understand what to do; Im not geting it right after i do the domain i cant find the range and i cant plot it plotting is easy its just the equations
that confuse me like finding the (x,y) coordinate after im done with the equation and ready to plot it . please help me .
thanks ,
lorrie
Answer by rapaljer(4671)   (Show Source):
You can put this solution on YOUR website! The domain always refers to the x numbers, and the range always refers to the y numbers. Now, for the equation 2x+7y = 9, if you are being asked to find the domain and the range, the domain and range are both ALL REAL VALUES. However, if you are asked to find a few points, then you pick a value of x (that would be a number in the domain!) and PLUG IT IN! Then you would solve for y, and that would give you a number in the range. I'm afraid all this domain and range is fine for the mathematicians but it confuses ordinary folks and makes the math seem a lot harder than it really is!!
In this example, you can pick any values for x:
If x =0, then 0+7y = 9, so y = 9/7.
If x = 1, then 2 + 7y = 9, so 7y = 7, y = 1
If y = 0, then 2x + 0 = 9, so x = 9/2
This means that points are like (0, 9/7) or (1,1) or (9/2,0) are all points on this graph:
The graph looks like this if you plot these points:
R^2 at SCC
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