Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
4. Graphing Linear Equations in Standard Form
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Exercise 7 Page 133

Substitute 0 for one of the variables and solve for the other, twice.

x-intercept: 6
y-intercept: 4

Practice makes perfect

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

2x+3y=12
2x+3( 0)=12
2x=12
x=6

An x-intercept of 6 means that the graph passes through the x-axis at the point ( 6,0).

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.

2x+3y=12
2( 0)+3y=12
3y=12
y=4

A y-intercept of 4 means that the graph passes through the y-axis at the point (0, 4).