SOLUTION: Graph the 2 lines below; and from the graph, read off the point of intersection. y=2x+3 y=x+5

Algebra ->  Linear-equations -> SOLUTION: Graph the 2 lines below; and from the graph, read off the point of intersection. y=2x+3 y=x+5      Log On


   



Question 207312: Graph the 2 lines below; and from the graph, read off the point of intersection.
y=2x+3
y=x+5

Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!
Graph the 2 lines below; and from the graph, read off the point of intersection.
system%28y=2x%2B3%2Cy=x%2B5%29

Get 3 points on the first line:

Arbitrarily select, say, x = 0 and substitute 0 for x in the
first equation:

y=2x%2B3
y=2%280%29%2B3
y=0%2B3
y=3

So the first point on the first line is (x,y) = (0,3)

---

Arbitrarily select, say, x = -2 and substitute -2 for x in the
first equation:

y=2x%2B3
y=2%28-2%29%2B3
y=-4%2B3
y=-1

So the second point on the first line is (x,y) = (-1,-1)

---

Arbitrarily select, say, x = 3 and substitute 3 for x in the
first equation:

y=2x%2B3
y=2%283%29%2B3
y=6%2B3
y=9

So the third point of the first line is (x,y) = (3,9)

Plot those three points:



Get a ruler and draw a straight line through them:



---------

Get 3 points on the second line:

Arbitrarily select, say, x = 1 and substitute 1 for x in the
second equation:

y=x%2B5
y=%281%29%2B5
y=1%2B5
y=6

So the first point on the second line is (x,y) = (1,6)

---

Arbitrarily select, say, x = -1 and substitute -1 for x in the
second equation:

y=x%2B5
y=%28-1%29%2B5
y=-1%2B5
y=4

So the second point on the second line is (x,y) = (-1,4)

---

Arbitrarily select, say, x = 4 and substitute 4 for x in the
second equation:

y=x%2B5
y=%284%29%2B5
y=4%2B5
y=9

So the third point of the second line is (x,y) = (4,9)

Plot those three points:



Take your ruler and draw a straight line through
those three points:



Now take your ruler and draw 2 lines from the point
where the two lines cross, one directly to the x-axis
and one directly to the y-axis:



Notice that these last two lines hit the x-axis
at 2 and the y-axis at 7.  So the solution is

x=2, y=7, sometimes written

(x,y) = (2,7)

To check we substitute x=2 and y=7
in both equations:

y=2x%2B3
7=2%282%29%2B3
7=4%2B3
7=7

It checks the first equation.  Now let's see if
it checks the second equation.

y=x%2B5
7=2%2B5
7=7

So it checks both equations, so it is correct.

Edwin