The greatest value of n for which the determinant $Δ=\begin{vmatrix} 1 & 1 & 1 \\ {^nC_1} & {^{n+3}C_1}& {^{n+6}C_1}\\ {^nC_2} & {^{n+3}C_2}& {^{n+6}C_2}\end{vmatrix} $ is divisible by $3^n$ , is |
2 1 4 3 |
3 |
The correct answer is option (4) : 3 We have, $Δ =\frac{1}{2}\begin{vmatrix} 1 & 1& 1\\n & n+3 & n+6 \\ n(n-1) & (n+2)(n+3) & (n+5)(n+6)\end{vmatrix}$ $Δ =\frac{1}{2}\begin{vmatrix} 1 & 0 & 0\\n & 3 & 6 \\ n(n-1) & 6n+6 & 12n+30\end{vmatrix}$ $Δ =9\begin{vmatrix} 1 & 0 & 0\\n & 1 & 1 \\ n(n-1) & 2(n+1) & 2n+5\end{vmatrix}=27$ Clearly, $Δ= 27 $ is divisible by $3, 3^2 $ and $3^3$. Hence, $n=3 .$ |