Find the ratio in which 2x+3y+5z=1 divides the line joining the points (1, 0, −3) and (1, −5, 7).
2x+3y+5z=1 divides (1,0,−3) and (1,−5,7) in the ratio of k:1 at point P.
Then, P(k+1k+1,−5kk+1,7k−3k+1) which must satisfy 2x+3y+5z=1
⇒2(k+1k+1)+3(−5kk+1)+5(7k−3k+1)=1
⇒2k+2−15k+35k−15=k+1
⇒21k=14
⇒k=23
∴2x+3y+5z=1 divides (1,0,−3) and (1,−5,7) in the ratio of 2:3.