Question

If points (a,0)(0,b) and (1,1) are collinear, then find the value of 1/a+1/b=1

Answer 1

Use area of triangle form by these three points is equal to zero 

area of t triangle=1/2 {a (b-1)+0+1 (0-b)}
0=ab-a-b
a+b=ab
divide both side by ab

a/ab+b/ab=ab/ab

1/b+1/a=1
hence 
1/a+1/b=1