Sung taee L. answered 11/25/12
Teach Concepts, Thinking methods, Step by Step (Physics & Math)
Let's go little bit further.
x = ab therefore b = x/a ------------------(1)
y = 3b + a therefore b = (1/3)(y-1) ------(2)
From equation (1) and (2),
(1/3)(y-1) = x/a rearrange this equation gives
y = (3/a)x + 1
Therefore when x=0, y = 1 (Y intercept) and when y=0, x = -a/3 (X intercept)