McGraw Hill Glencoe Algebra 1, 2012
MH
McGraw Hill Glencoe Algebra 1, 2012 View details
1. Graphing Linear Equations
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Exercise 58 Page 161

Practice makes perfect
a We are given a variety of lines that we have been asked to create on a coordinate plane. Let's go through the different lines one at a time.

x- and y-intercept

Any line that is not a vertical or a horizontal line has an x-intercept and a y-intercept.

Graph of a line slanting down. Its x- and y-intercepts are marked

x-intercept, No y-intercept

A line with only an x-intercept is a line of the form x=a, where a≠0. These are known as vertical lines. The line x=1 does not have any y-intercepts but has exactly one x-intercept.

Graph of x=1. Its x-intercept is marked

Exactly 2 x-intercepts

This is impossible. Lines are straight, and cannot bend or change direction. Therefore, no line can cross the x-axis twice.

No x-intercept, One y-intercept

A line with no x-intercept is a horizontal line of the form y=a, where a≠ 0. An example of this is shown below.

Graph of y=1. Its y-intercept is marked

Exactly 2 y-intercepts

This is impossible for the same reason a line cannot have two x-intercepts.

b Let's consider our results from Part A.
  • It is possible to draw a line that has one x-intercept and one y-intercept. Any line with a positive or negative slope will do it.
  • It is also possible to draw a line with only one x-intercept and no y-intercept. Any vertical line that does not coincide with the y-axis will work.
  • It is not possible to draw a line with exactly two x-intercepts. Only a curve will satisfy such a condition.
Graph of a curve that has two x-intercepts. The x-intercepts are marked


  • It is also possible to draw a line with only one y-intercept and no x-intercept. Any horizontal line that does not coincide with the y-axis will work.
  • It is not possible to draw a line with exactly two y-intercepts. Only a curve such as the one below will satisfy such a condition.
Graph of a curve that has two y-intercepts. The y-intercepts are marked
c When a line is drawn in a coordinate system it can have at most one intercept per axis. In fact, a line must intercept at least one of the axes.