SOLUTION: how do you solve sytems of equations by graphing? here is an example that my math book gives me: y=2x+4 I have so much trouble tryng to solve these. x+y=-2.

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Question 30599: how do you solve sytems of equations by graphing? here is an example that my math book gives me: y=2x+4 I have so much trouble tryng to solve these.
x+y=-2.
I also have trouble tyring to use substitution to solve problems such as this:
y=2x-3 Please help me my math grade is going down drastically!!!!!!!
y=0

Answer by Cintchr(481) (Show Source):
You can put this solution on YOUR website!
and
The first equation is in the proper form. Lets get the 2nd one in that form, too.
solve for y

Let's look at both equations. They are in y=mx+b format.
the b is the y-intercept
the m is the slope (rise/run)
equation #1 has a y-inter. of +4 and a slope of 2/1
equation #1 has a y-inter. of -2 and a slope of -1/1
to plot the first ...
start at the origin and go up to +4.
place a dot here at (0,4)
from here go up 2 and right 1 (rise/run) place another dot.
Go back to (0,4)
go down 2 and back 1 and place another dot.
connect these three points.

now for the second line.
starting at the origin, go down 2 and place a point (0, -2)
from here go down one and to the right one. Place a dot here.
go back to (0, -2)
go up one and left one.
place a third dot here.

continue out the lines so that they cross. This is the solution for the system

now for substitution:
and
the second equation tells you what to put in place of y in the first equation
solve for x

your ordered pair (solution) is (x, y)
(3/2, 0)