[" 16.The maximum sum of the series "20+19(1)/(3)+18(2)/(3)+..." is "],[[" (c) "tan a_(1)-tan a_(n)," 26."],[" (a) "310," (b) "300],[" (c) "320," (d) None of these "]]

The maximum sum of the series 20 +19(1)/(3)+18 (2)/(3) + cdots is

The minimum sum of the series : 20 + 19(1)/(3)+ 18(2)/( 3) +"..." is :

In a series a_(n) = (n(n+1))/(3), a_(2) = ………….

The sum of 19 terms for AP. a_(1),a_(2),....a_(19) & given a_(4)+a_(8)+a_(12)+a_(16)=224, is

If a_(1), a_(2), a_(3),…, a_(40) are in A.P. and a_(1) + a_(5) + a_(15) + a_(26) + a_(36) + a_(40) = 105 then sum of the A.P. series is-

Let a_(1),a_(2),a_(3)"……." be an arithmetic progression and b_(1), b_(2), b_(3), "……." be a geometric progression sequence c_(1),c_(2),c_(3,"…." is such that c_(n)= a_(n) + b_(n) AA n in N . Suppose c_(1) = 1, c_(2) = 4, c_(3) = 15 and c_(4) = 2 . The value of sum of sum_(i = 1)^(20) a_(i) is equal to "(a) 480 (b) 770 (c) 960 (d) 1040"

If a_(1), a_(2), a_(3),…….,a_(20) are in AP and a_(1) + a_(20) = 45 , then a_(1) + a_(2) + a_(3)+……+a_(20) is equal to

If (1+x+x^(2))^(n) = sum_(r=0)^(2 n) a_(r). x^(r) then a_(1)-2 a_(2)+3 a_(3)-..-2 n. a_(2n) =