Homework Tips for Graphing


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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