Question

if the points a(x,y), b(a,0), c(0,b) are collinear, prove x/a+y/b =1

Answer 1

if three points are colinear then area of triangle form by these points equal zero.

now
area of triangle=1/2 {x (0-b)+a (b-y)+0}
0=-bx+ab-y
ay+bx=ab
now divide both side by ab

ay/ab+bx/ab=ab/ab

y/b+x/a=1
hence
x/a+y/b=1

Answer 2

i hope this will usful to u