Exercise 12 Page 541

To determine the x-intercept of a line, we need to substitute 0 for y and solve. In this case, we haven't been given an equation, so we will need to use the given points to write one.

Writing the Equation

The quickest way to write an equation when given two points is by using the point-slope form. An equation in point-slope form follows a specific format. y- y_1= m(x- x_1)In this form, m is the slope and the point ( x_1, y_1) lies on the graph of the line. To create our equation, we can use either of the given points for x_1 and y_1 as well as the slope. To calculate the slope, we will use the Slope Formula.

Using the point ( 0, -4) as our point and the slope 8, we have everything needed to form a point-slope form equation. y-( -4)= 8(x- 0) ⇔ y+4=8x Note that there are infinitely many correct ways to write this equation in point-slope form, as long as we use a point that lies on the line.

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.

An x-intercept of 12 means that the graph passes through the x-axis at the point ( 12,0).