Question

If the slope of the line joining the points (3, -9) and (p, 2p + 3) is -5/7 then find the value of p

• A. $\frac{23}{4}$
• B. $\frac{9}{4}$
• C. $\frac{-69}{19}$
• D. $\frac{-99}{4}$

Answer 1

The correct option is C $\frac{-69}{19}$

Slope of line joining two points $(x_1,y_1)$ and $(x_2,y_2)$ is $\frac{y_2-y_1}{x_2-x_1}$
So, Slope of line joining $(3,-9);(p,2p+3)$ is $\frac{2p+3+9}{p-3}=-\frac{5}{7}$
$=>\frac{2p+12}{p-3}=-\frac{5}{7}$
$=>14p+84=-5p+15$
$=>19p=-69$
$=>p=-\frac{69}{19}$