Chapter 4, Problem 35SGR

To determine

To Write: An equation of line in slope intercept form that passes through point $\left(1,3\right)$ and is parallel to line $y=-2x-4$

Answer to Problem 35SGR

An equation of line in slope- intercept form is $y=-2x+5$

Explanation of Solution

Given information:

Line passes through point $\left(1,3\right)$ and is parallel to line $y=-2x-4$

Concept and Formula Used:

Slope intercept form $y=mx+c$ where $m$ is slope and $c$ is intercept.

Point slope form of a line: $y-y_1=m\left(x-x_1\right)$

Parallellines: If lines are parallel then the slopes of lines are equal

Calculation:

The required line is parallel to

  $y=-2x-4$

Now, find the slope of given line by comparing it with $y=mx+c$ .

The slope of line $y=-2x-4$ is $m=-2$ .

Let the slope of required line be ‘m’. As the required line is parallel to $y=-2x-4$

Therefore, the slope of required line is equal to slope of $y=-2x-4$ i.e. $m=-2$

The required line passes through $\left(1,3\right)$ and having slope $-2$ . Using point slope form of equation of line

  $\begin{array}{l}y-y_1=m\left(x-x_1\right)\\ \text{where }\left(x_1,y_1\right)=\left(1,3\right)\&m=-2\\ y-3=-2\left(x-1\right)\\ y-3=-2x+2\left(\text{Distributive property}\right)\\ \text{Add 3 on both sides}\\ y-3+3=-2x+2+3\\ y=-2x+5\end{array}$

Conclusion:

An equation of line in slope- intercept form is $y=-2x+5$