**Recognize equations of horizontal and vertical lines.**

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A graph can fail to have an *x*-intercept or a *y*-intercept, which is why the phrase “if any” was added when discussing intercepts.

**Graphing a Horizontal Line**

Graph *y *= 2.

Since *y *is always 2, there is no value of *x *corresponding to *y * = 0, so the graph has no *x*-intercept. The *y*-intercept is (0, 2). The graph in Figure 7, shown with a table of ordered pairs, is a horizontal line.

**Graphing a Vertical Line**

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Graph *x *+ 1 =0.

The *x*-intercept is (-1, 0). The standard form 1*x *+ 0*y* = -1 shows that every value of *y *leads to *x *= – 1, so no value of *y *makes *x *= 0. The only way a straight line can have no *y*-intercept is if it is vertical.