If the points A(1,2),B(0,0)andC(a,b) are collinear ,then what is the relation between a and b

If the points A(1,2),B(0,0)andC(a,b) are collinear ,then what is the r

1.	If the points A(1,2),B(0,0)andC(a,b) are collinear ,then what is the relation between a and b
Answer» 2a=b