Use the Slope–Intercept Form of an Equation of a Line: example 4.52

Use slopes and y-intercepts to determine if the lines $y = −4$ and $y = 3$ are parallel.

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.

Use slopes and y-intercepts to determine if the lines $y = 8 and y = −6$ are parallel.

How did it go?

	$\begin{matrix} y = −4 \\ y = 0 x - 4 \end{matrix}$	and	$\begin{matrix} y = 3 \\ y = 0 x + 3 \end{matrix}$
Write each equation in slope-intercept form.	$y = 0 x - 4$		$y = 0 x + 3$
Since there is no $x$ term we write $0 x$ .	$y = m x + b$		$y = m x + b$
Identify the slope and $y$ -intercept of both lines.	$m = 0$		$m = 0$
	$y -intercept is (0, 4)$		$y -intercept is (0, 3)$

	$\begin{matrix} y = −4 \\ y = 0 x - 4 \end{matrix}$	and	$\begin{matrix} y = 3 \\ y = 0 x + 3 \end{matrix}$
Write each equation in slope-intercept form.	$y = 0 x - 4$		$y = 0 x + 3$
Since there is no $x$ term we write $0 x$ .	$y = m x + b$		$y = m x + b$
Identify the slope and $y$ -intercept of both lines.	$m = 0$		$m = 0$
	$y -intercept is (0, 4)$		$y -intercept is (0, 3)$