Exercise 20 Page 172

We will graph this equation by finding and plotting its intercepts. Then, we will connect them with a line. To find the x- and y-intercepts, we will need to substitute 0 for one variable and solve. After that, 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 equal to 0, and the x-value is the x-intercept. To find the x-intercept of the given equation, we should substitute 0 for y. Then, solve for x.

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

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.

3x-4y=- 12

Substitute

x= 0

3( 0)-4y=- 12

ZeroPropMult

Zero Property of Multiplication

-4y=- 12

DivEqn

.LHS /(- 4).=.RHS /(- 4).

y=3

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

Graphing the Equation

We can now graph the equation by plotting the intercepts and connecting them with a line.