Question

Find the value of r so the line that passes through (-5,2) and (3,r) has a slope of -1/2

Answer 1

The value of r so the line that passes through (-5,2) and (3,r) has a slope of -1/2 is -2

Solution:

Given that line is passing through point (-5, 2) and (3, r)

Slope of the line is $\frac{-1}{2}$

Need to determine value of r.

Slope of a line passing through point $\left(x_{1}, y_{1}\right) \text { and }\left(x_{2}, y_{2}\right)$  is given by following formula:

$\text { Slope } m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$  --- eqn 1

$\text { In our case } x_{1}=-5, y_{1}=2, x_{2}=3, y_{2}=\mathrm{r} \text { and } m=-\frac{1}{2}$

On substituting the given value in (1) we get

$\begin{array}{l}{-\frac{1}{2}=\frac{r-2}{3-(-5)}} \\\\ {\text { Solving the above expression to get value of } r} \\\\ {=>-\frac{1}{2}=\frac{r-2}{3+5}} \\\\ {=>-8=\frac{r-2}{3+5}} \\\\ {=>-8=2(r-2)} \\\\ {=>-8=2 r-4} \\\\ {=>2 r=-8+4} \\\\ {=>2 r=-4} \\\\ {=>r=\frac{-4}{2}=-2}\end{array}$

Hence the value of "r" is -2