formula needed:
Division of segment between P1(x1,y1) and P2(x2,y2) in a ratio a:b.
Coordinates of point of division
[tex](x1+(x2-x1)\frac{a}{a+b}, y1+(y2-y1)\frac{a}{a+b})[/tex]
For the given problem,
C(x1,y1)=C(9,6)
D(x2,y2)=D(5,1)
ratio a:b= 4:1 => a=4, b=1, a+b=5
Point of division
=[tex](x1+(x2-x1)\frac{a}{a+b}, y1+(y2-y1)\frac{a}{a+b})[/tex]
=[tex](9+(5-9)\frac{4}{4+1}, 6+(1-6)\frac{4}{4+1})[/tex]
=[tex](9 - 4\frac{4}{5}, 6 - 5\frac{4}{5})[/tex]
=[tex](5\frac{4}{5}, 2)[/tex]
=(29/5, 2)