Determine the ratio in which the point P (m, 6) divides the join of A(−4, 3) and B(2, 8). Also, find the value of m.
The co-ordinates of a point which divided two points $\left(x_{1}, y_{1}\right)$ and $\left(x_{2}, y_{2}\right)$ internally in the ratio $m: n$ is given by the formula,
$(x, y)=\left(\left(\frac{m x_{2}+n x_{1}}{m+n}\right),\left(\frac{m y_{2}+n y_{1}}{m+n}\right)\right)$
Here we are given that the point P(m,6) divides the line joining the points A(−4,3) and B(2,8) in some ratio.
Let us substitute these values in the earlier mentioned formula.
$(m, 6)=\left(\left(\frac{m(2)+n(-4)}{m+n}\right),\left(\frac{m(8)+n(3)}{m+n}\right)\right)$
Equating the individual components we have
$6=\left(\frac{m(8)+n(3)}{m+n}\right)$
$6 m+6 n=8 m+3 n$
$2 m=3 n$
$\frac{m}{n}=\frac{3}{2}$
We see that the ratio in which the given point divides the line segment is.
Let us now use this ratio to find out the value of ‘m’.
$(m, 6)=\left(\left(\frac{m(2)+n(-4)}{m+n}\right),\left(\frac{m(8)+n(3)}{m+n}\right)\right)$
$(m, 6)=\left(\left(\frac{3(2)+2(-4)}{3+2}\right),\left(\frac{3(8)+2(3)}{3+2}\right)\right)$
Equating the individual components we have
$m=\frac{3(2)+2(-4)}{3+2}$
$m=-\frac{2}{5}$
Thus the value of ' $m$ ' is $-\frac{2}{5}$.