2010
A
first degree equation is
called a linear equation in two
variables if it contains two
distinct variables.
 1.
Arbitrarily select some
points that satisfy the
equation.
 2. Plot the points in a
coordinate plane.
 3. Draw the line passing
through these points. This is
the graph of the equation.

Graph y = 2x + 3.
 Plotting
the x-intercept and yintercept of a graph and
drawing a line through them is
called the intercept method of
graphing a linear equation.

Graph y = 2x + 4.
 Set
of two or more equations
is called a system of
equations.
 Consider
the following system
of equations:
y – 2x = –6
y + x = –3
To solve the system, we can
first graph each equation.
 In
order to solve a system of
equations we can write the
equations in a way that eliminates
one of the unknowns. Then the
remaining equality will be in one
unknown, and we can solve this
easily. This method is called the
elimination method.
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1. Write the given equations in the form Ax + By
= C.
2. Take one equation. Make the coefficient of the
variable which you want to eliminate the additive
inverse of the same variable in the other
equation.
3. Add the resulting equations to eliminate your
chosen variable.
4. Solve the resulting equation in one unknown.
5. Find the other variable by substituting this
solution into either original equation.
6. Check your result.
 Another
method for solving
systems of equations is the
substitution method.
1. Solve one of the equations for one
variable in terms of the other variable.
 2. Substitute the resulting expression
into the other equation and solve.
 3. Find the other variable by substituting
the result of step 2 into either original
equation.
 4. Check your result.
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