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The two-dimensional **Cartesian coordinate system** may be used to graph a variety of equations in the form of straight and curved lines. One way to graph an equation is to determine a number of different values for the variables and plot them on the graph. It can be helpful, however, to understand how a change in the **parameters** of an equation affects the resulting line.

## Graphs of Straight Lines

The graph of the simple equation *y* = 1*x*, or *y = x*, is graphed in (a) below. The line passes through every coordinate point where *x = y*, such as (2, 2) or (–3, –3).

Notice what happens to the graph of the equation when the parameters of the equation are changed by using a different coefficient for x, such as *y* = 3*x*. As part (a) shows, the new line has a steeper slope. If...

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