Chapter 4.1, Problem 8MRE

a.

To determine

The slope of the line containing the points $\left(-4,7\right),\left(1,9\right)$ .

Answer to Problem 8MRE

The value of slope is $\frac{2}{5}$ .

Explanation of Solution

Given information: The two points contained by line are $\left(-4,7\right),\left(1,9\right)$ .

Formula Used: The slope $\left(m\right)$ of line through two points $\left(x_1,y_1\right),\left(x_2,y_2\right)$ is given as,

  $m=\frac{y_2-y_1}{x_2-x_1}$

Calculation: The slope of the line through the points $\left(-4,7\right),\left(1,9\right)$ is evaluated using the formula as,

  $\begin{array}{c}m=\frac{9-7}{1+4}\mathrm{....}\left(\begin{array}{l}\left(x_1,y_1\right)\to \left(-4,7\right)\\ \left(x_2,y_2\right)\to \left(1,9\right)\end{array}\right)\\ =\frac{2}{5}\mathrm{......}\left(1\right)\end{array}$

Hence the slope of the line is $\frac{2}{5}$ .

b.

To determine

The equation of the line in standard form through the points $\left(-4,7\right),\left(1,9\right)$ .

Answer to Problem 8MRE

The equation of line in standard form is $\text{2}x-5y=-43$ .

Explanation of Solution

Given information: The two points contained by line are $\left(-4,7\right),\left(1,9\right)$ .

Formula Used: The equation of line having slope $\left(m\right)$ and through the point $\left(x_1,y_1\right)$ is given as,

  $y-y_1=m\left(x-x_1\right)$

Calculation: The equation of the line through the point $\left(-4,7\right)$ and having slope $\left(m=\frac{2}{5}\right)$ from (1) is evaluated using the formula as,

  $\begin{array}{c}y-y_1=m\left(x-x_1\right)\\ y-7=\left(\frac{2}{5}\right)\left(x+4\right)\mathrm{....}\left(\begin{array}{l}\left(x_1,y_1\right)\to \left(-4,7\right)\\ m=\frac{2}{5}\text{ from }\left(1\right)\end{array}\right)\\ 5y-35=2x+\mathrm{8......}\left(\begin{array}{l}\text{Cross-multiply}\\ \text{and simplified}\end{array}\right)\\ \text{or, 2}x-5y=-\mathrm{43......}\left(\begin{array}{l}\text{Standard form}\\ ax+by=c\end{array}\right)\end{array}$