If `n` is an integer between 0 and 21, then the minimum value of `n!(21-n)!` is attained for `n=` `1` b. `10` c. `12` d. `20`

If 1/2,1/3,n are the direction cosines of a line , then the value of n is

If (a^(n)+b^n)/ (a^(n-1) +b^(n-1)) is the A.M. between a and b, then find the value of n.

If ^n P_r=^n P_(r+1)a n d^n C_r=^n C_(r-1,) then the value of n+r is.

If n(A)=10 and n(B)=15 then the minimum and maximum number of elements in AnnB is

If cot^(-1)n/pi>pi/6,n in N , then the maximum value of n is 6 (b) 7 (c) 5 (d) none of these

If ^n C_r=84 ,^n C_(r-1)=36 ,a n d^n C_(r+1)=126 , then find the value of ndot

If a_1,a_2, .....,a_n are positive real numbers whose product is a fixed number c , then the minimum value of a_1+a_2+.........+a_(n-1)+2a_n is a. a_(n-1)+2a_n b. (n+1)c^(1//n) c. 2n c^(1//n) d. (n)(2c)^(1//n)

Suppose A is a complex number and n in N , such that A^n=(A+1)^n=1, then the least value of n is a. 3 b. 6 c. 9 d. 12