Question 622447: y=4x+4
3x+2y=12
solve this as a linear equation and graph. don't know how to answer this. please help.
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website!  is a linear equation.
So is 
Linear equations involve one or more variables (usually x, and/or y, and/or z) with no exponents.
A linear equation involving only one or two variables can be graphed as a straight line. (If a linear equation has three or more variables, you cannot graph it).
 is a system of linear equations with two variables.
There are several ways to solve such a system of linear equations. Sometimes you can use graphing to get to the solution. Even when graphing does not lead you to the solution, a graph may help to figure out the problem.
Each equation can be graphed as a line.
If the lines are parallel, there is no solution.
If the same line is the graph for both equations, all the points in that line represent the infinite solutions to the system of equations.
If the lines intersect, the intersection point represents the unique solution to the system. In that case, if the values for x and y that correspond to the intersection can be clearly read from the graph, you have a tentative solution. It still needs to be verified by substituting into the equations.
GRAPHING THE SYSTEM:To graph each line, you need only two points.
You can chose any points, but you may want to chose points that make calculations easy and give you a convenient graph. (You can often get good points by making x=0 and/or y=0).
For equation :
 -->  -->  gives you point (0,6).
 -->  -->  gives you point (4,0).
The graph for that line (with circles around the points used) is:
For equation :
-->  gives you point (0,4).
-->  -->  -->  gives you point (-1,0).
The graph for the whole system, with the new line graphed in green, looks like this:
 We see that there is one point that represents the solution, but can only make a wild guess about the coordinates of that point.
SOLVING BY SUBSTITUTION:
gives you an expression for  that can be substituted into
to get
 -->  -->  -->  -->  -->  --> 
Now we substitute that value into to get
 -->  -->  or 
So the intersection of those two lines is the point with
 and  .
We could never have figured that out from the graph.
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