#### Find the coordinates of the point R on the line segment joining the points P(–1, 3) and Q(2, 5) such that $PR= \frac{3}{5}PQ$

Solution

$section\, formula \left ( \frac{m_{1}x_{2}+m_{2}x_{1}}{m_{1}+m_{2}},\frac{m_{1}y_{2}+m_{2}y_{1}}{m_{1}+m_{2}} \right )$
According to question let R = (x, y) and PR = $\frac{3}{5}$ PQ
$\frac{PQ}{PR}= \frac{3}{5}$
R lies on PQ                $\therefore$ PQ = PR +RQ

$\frac{PR+PQ}{PR}= \frac{5}{3}$
On dividing separately we get
$1+\frac{RQ}{PR}= \frac{5}{3}$
$\frac{RQ}{PR}= \frac{5}{3}-1= \frac{2}{3}$
$\Rightarrow PR:RQ= 3:2$
Hence, R divides PQ in ratio 3 : 2 using section formula we have
(x1, y1) = (-1, 3)                       (x2, y2) = (2, 5)
m1 = 3, m2 = 2
$R\left ( x,y \right )= \left ( \frac{3\left ( 2 \right )+2\left ( -1 \right )}{3+2} ,\frac{3\left ( 5 \right )+2\left ( 3 \right )}{3+2}\right )$
$R\left ( x,y \right )= \left ( \frac{6-2}{5},\frac{15+6}{5} \right )$
$R\left ( x,y \right )= \left ( \frac{4}{5},\frac{21}{5} \right )$
Here co- ordinates of R is $\left ( \frac{4}{5},\frac{21}{5} \right )$