Question

if the points (x,1) (1,2) and (0, y+1) are collinear
Show that
1/x + 1/y =1
​

Answer 1

Area of triangle = 0
x [ 2- ( y + 1)] + 1 ( y + 1 -1 ) + 0 ( 1 -2 )= 0
x - xy + y = 0
( divide by xy )
1/y -1 + 1/x = 0
1/y + 1/x = 1
Thus proved