Use the Slope–Intercept Form of an Equation of a Line: example 4.44

Graph the line of the equation $y = − x + 4$ using its slope and y-intercept.

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Graph the line of the equation $y = − x - 3$ using its slope and y-intercept.

How did it go?

	$y = m x + b$
The equation is in slope–intercept form.	$y = − x + 4$
Identify the slope and y-intercept.	$m = −1$
	y-intercept is (0, 4)
Plot the y-intercept.	See graph below.
Identify the rise and the run.	$m = \frac{−1}{1}$
Count out the rise and run to mark the second point.	rise −1, run 1
Draw the line.
To check your work, you can find another point on the line and make sure it is a solution of the equation. In the graph we see the line goes through (4, 0).
Check. $\begin{matrix} y & = & − x + 4 \\ 0 & \overset{?}{=} & - 4 + 4 \\ 0 & = & 0 ✓ \end{matrix}$

	$y = m x + b$
The equation is in slope–intercept form.	$y = − x + 4$
Identify the slope and y-intercept.	$m = −1$
	y-intercept is (0, 4)
Plot the y-intercept.	See graph below.
Identify the rise and the run.	$m = \frac{−1}{1}$
Count out the rise and run to mark the second point.	rise −1, run 1
Draw the line.
To check your work, you can find another point on the line and make sure it is a solution of the equation. In the graph we see the line goes through (4, 0).
Check. $\begin{matrix} y & = & − x + 4 \\ 0 & \overset{?}{=} & - 4 + 4 \\ 0 & = & 0 ✓ \end{matrix}$