The first 3 terms in the expansion of (1+ax)n (n ≠ 0) are 1, 6x and 16x2. Then the value of a and n are respectively
2 and 9
3 and 2
2/3 and 9
3/2 and 6
nc1.ax=6x;nc2(ax)2=16x2⇒an=6;n(n−1)2a2=16⇒a=23⇒n=9