The value of `1+2+3+......+n`
(a) `(n(n+1))/(2)`
(b) `(n(a+l))/(2)`
(c) `(n(n-1))/(2)`
(d) `(n(n+1)(n+2))/(3)`

The mean deviation of the series a , a+d , a+2d ,.....,a+2n from its mean is (a) ((n+1)d)/(2n+1) (b) (n d)/(2n+1) (c) (n(n+1)d)/(2n+1) (d) ((2n+1)d)/(n(n+1))

The mean deviation of the series a , a+d , a+2d , , a+2n from its mean is ((n+1)d)/(2n+1) (b) (n d)/(2n+1) (c) (n(n+1)d)/(2n+1) (d) ((2n+1)d)/(n(n+1))

The arithmetic mean of 1,2,3,...n is (a) (n+1)/2 (b) (n-1)/2 (c) n/2 (d) n/2+1

The arithmetic mean of 1,2,3,...n is (a) (n+1)/2 (b) (n-1)/2 (c) n/2 (d) n/2+1

(d^n)/(dx^n)(logx)=? (a) ((n-1)!)/(x^n) (b) (n !)/(x^n) (c) ((n-2)!)/(x^n) (d) (-1)^(n-1)((n-1)!)/(x^n)

If n is a non zero rational number then show that 1 + n/2 + (n (n - 1))/(2.4) + (n(n-1)(n - 2))/(2.4.6) + ….. = 1 + n/3 + (n (n + 1))/(3.6) + (n (n + 1) (n + 2))/(3.6.9) + ….

Let the sequence a_1,a_2,a_3, ,a_n from an A.P. Then the value of a1 2-a2 2+a3 2-+a2n-1 2-a2n2 is (2n)/(n-1)(a2n2-a1 2) (b) n/(2n-1)(a1 2-a2n2) n/(n+1)(a1 2-a2n2) (d) n/(n-1)(a1 2+a2n2)

The standard deviation of the data: x : , 1, a , a^2 , ..., a^n f: , ^n C_0 , ^n C_1 , ^n C_2 , ..., ^n C_n is ((1+a^2)/2)^n-((1+a)/2)^(2n) (b) ((1+a^2)/2)^(2n)-((1+a^2)/2)^(2n) (c) ((1+a)/2)^(2n)-((1+a^2)/2)^n (d) none of these

1+n. (2n)/(1+n)+(n(n+1))/(1.2) ((2n)/(1+n))^2+…..

The value of ""(n)C_(1). X(1 - x )^(n-1) + 2 . ""^(n)C_(2) x^(2) (1 - x)^(n-2) + 3. ""^(n)C_(3) x^(3) (1 - x)^(n-3) + ….+ n ""^(n)C_(n) x^(n) , n in N is