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Determining if Ordered Pairs are Solutions
to Equations
If given an ordered pair, substitute in the equation and if you get a true statement the pair is a solution to
the equation.
To
complete an ordered pair so that it is a solution to an equation, sustitute the x value or y value into the equation
and solve for the other variable.
Plotting a Point
The
rectangular coordinate system is made up of two number lines, one horizontal called the x axis and one vertical called the y axis. A point consists of an ordered pair. The
first coordionate is always the x value
and the second
coordinate is always the y value.
In
order to plot a point, start at the origin(0,0). move horizontally (right or left depending on the sign of x) the
number of units of the x coordinate and go vertically (up of down depending on the y coordinate). Now plot your
point. It takes TWO coordinates to plot a point.
Graphing a Straight Line
Draw
a "t" table for the values of x and y.We want to find three points on the line.
First,
make x = 0 and find the y value when x = 0 by substituting in
the equation.
Next,
make y = 0 and substitute in the equation to find the value of
x when y = 0.
Connect the two points and draw the line.If we only use these two point we are graphing using the intercept
method. The x intercept is where the line touches the x axis (y=0)
and the y intercept is where the line touches the y axis (x = 0). We should use a third point to make sure we have
not made an error. Now, make x or y anything you wish and substitute back into the equation to get your third point.
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