4. Graphing a Function Rule
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Substitute some arbitrary values for x to find their corresponding y-values.
One way to graph a function rule is by making a table of values and substituting some arbitrary values for x. Doing so will give the corresponding values of y, which we can use to form ( x, y) coordinate pairs.
| x | -2x^2 | y | (x,y) |
|---|---|---|---|
| -2 | -2( -2)^2 | -8 | ( -2, -8) |
| -1 | -2( -1)^2 | -2 | ( -1, -2) |
| 0 | -2( 0)^2 | 0 | ( 0, 0) |
| 1 | -2( 1)^2 | -2 | ( 1, -2) |
| 2 | -2( 2)^2 | -8 | ( 2, -8) |
By connecting all of our points with a line, we form the graph of the function rule. Because there is a variable with an exponent in the function, our line will not be straight. Later, we will learn that this type of function is called a cuadratic function and this type of graph is called a parabola.