Solve Systems by Graphing
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Transcript Solve Systems by Graphing
Objective
The student will be able to:
solve systems of equations by graphing.
What is a system of equations?
A system of equations is when you have two
or more equations using the same variables.
A system of two linear equations in two
variables x and y has the form: y = mx + b
A solution to a system of linear equations
in two variables is an ordered pair that
satisfies both equations in the system.
When graphing, you will encounter three
possibilities.
Solving a system of linear equations
by graphing
Rewrite each equation in slopeintercept form – y=mx + b.
Determine the slope and y-intercept and
use them to graph each equation.
The solution to the linear system is the
ordered pair where the lines intersect.
Intersecting Lines
The point where the lines
intersect is your solution.
The solution of this graph
is (1, 2)
(1,2)
Examples
Y = 1/2x + 5
Y = -5/2x - 1
Examples
Y = -3/2x + 1
Y = 1/2x - 3
Parallel Lines
These lines never
intersect!
Since the lines never
cross, there is
NO SOLUTION!
Parallel lines have the
same slope with different
y-intercepts.
2
Slope = = 2
1
y-intercept = 2
y-intercept = -1
Coinciding Lines
These lines are the same!
Since the lines are on top
of each other, there are
INFINITELY MANY
SOLUTIONS!
Coinciding lines have the
same slope and
y-intercepts.
2
Slope = = 2
1
y-intercept = -1
How many solutions?
Y = 2/3x - 5
Y = 2/3x + 1
How many solutions?
Y = 3x - 12
Y = 1/8x - 12
How many solutions?
Y = 5/3x - 2
Y = 10/6x - 2
Solving a system of equations by graphing.
Let's summarize! There are 3 steps to
solving a system using a graph.
Step 1: Graph both equations.
Graph using slope and y – intercept
or x- and y-intercepts. Be sure to use
a ruler and graph paper!
Step 2: Do the graphs intersect?
This is the solution! LABEL the
solution!
Step 3: Check your solution.
Substitute the x and y values into
both equations to verify the point is a
solution to both equations.