Big Ideas Math Integrated I, 2016
BI
Big Ideas Math Integrated I, 2016 View details
4. Graphing Linear Equations in Standard Form
Continue to next subchapter

Exercise 10 Page 133

You will need to substitute 0 for one of the variables and solve, twice.

x-intercept: 3
y-intercept: -2

Practice makes perfect

To determine the x- and y-intercepts of a line, we need to substitute 0 for one variable, solve, then repeat for the other variable.

Finding the x-intercept

Think of the point where the graph of an equation crosses the x-axis. The y-value of that ( x, y) coordinate pair is 0, and the x-value is the x-intercept. To find the x-intercept of the equation, we should substitute 0 for y and solve for x.

-6x+9y=-18
-6x+9( 0)=-18
-6x=-18
x=3

An x-intercept of 3 means that the graph passes through the x-axis at the point ( 3,0).

Finding the y-intercept

Let's use the same concept to find the y-intercept. Consider the point where the graph of the equation crosses the y-axis. The x-value of the ( x, y) coordinate pair at the y-intercept is 0. Therefore, substituting 0 for x will give us the y-intercept.

-6x+9y=-18
-6( 0)+9y=-18
9y=-18
y=-2

A y-intercept of -2 means that the graph passes through the y-axis at the point (0, -2).