Exercise 4 Page 177

To determine the x-intercept for the given equation, we will substitute 0 for y and solve for x. To determine the y-intercept, we will substitute 0 for x and solve for y.

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. Consider the given equation. -4x-5y=40Let's substitute 0 for y and solve for x.

-4x-5y=40

Substitute

y= 0

-4x-5( 0)=40

ZeroPropMult

Zero Property of Multiplication

-4x=40

DivEqn

.LHS /-4.=.RHS /-4.

x=-10

The x-intercept of the equation is -10.

Finding the y-intercept

In the same way as above, now 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.

-4x-5y=40

Substitute

x= 0

-4( 0)-5y=40

ZeroPropMult

Zero Property of Multiplication

-5y=40

DivEqn

.LHS /-5.=.RHS /-5.

y=-8

The y-intercept of the equation is -8.