Segment in the direction from A to C
Initial Point: A=(9,5)=(xa,ya)→xi=xa=9, yi=ya=5
Final point: C=(-7,1)=(xc,yc)→xf=xc=-7, yf=yc=1
B=(xb,yb)=?
Proportion: r=AB/BC=3:1=3/1→r=3
xb=(xi+r*xf)/(1+r)
Replacing xi=xa=9, xf=xc=-7 and r=3
xb=[9+3*(-7)]/(1+3)
xb=(9-21)/4
xb=(-12)/4
xb=-3
yb=(yi+r*yf)/(1+r)
Replacing yi=ya=5, yf=yc=1 and r=3
yb=[5+3*(1)]/(1+3)
yb=(5+3)/4
yb=8/4
yb=2
B=(xb,yb)→B=(-3,2)
Answer: B=(-3,2)