If `1/(1+2x+x^2)= 1+a_1x+a_2x^2+…..` then the value of `a_r` is (A) `2` (B) `r+1` (C) `r` (D) `2r`

If cotA+cotB+cotC = k(1/x^2+1/y^2+1/z^2) then the value of k is (A) R^2 (B) 2R (C) /_\ (D) a^2+b^2+c^2

If (1+2x+3x^2)^10=a_0+a_1x+a_2x^2+……..+a_20x^20 then (A) a_1=20 (B) a_2=210 (C) a_3=1500 (D) a_20=2^3.3^7

Let f: R to R be defined by f(x)=(x)/(1+x^(2)), x in R. Then, the range of f is (A) [-(1)/(2),(1)/(2)] (B) (-1,1)-{0} (C) R-[-(1)/(2),(1)/(2)] (D) R-[-1,1]

If C_(r) be the coefficients of x^(r) in (1 + x)^(n) , then the value of sum_(r=0)^(n) (r + 1)^(2) C_(r) , is

If A_r=|[1,r,2^r],[2,n,n^2],[n,(n(n+1))/2, 2^(n+1)]|, the value of sum_(r=1)^n A_r is (A) n (B) 2n (C) -2n (D) n^2

Let (1+x^2)^2(1+x)^n=A_0+A_1x+A_2x^2+…."if" A_0A_1A_2 are in A.P then the value of n is

If (4x^(2) + 1)^(n) = sum_(r=0)^(n)a_(r)(1+x^(2))^(n-r)x^(2r) , then the value of