下列级数绝对收敛的是()A.sum _(n=1)^infty dfrac ({(-1))^n+1}(2n+1)B.sum _(n=1)^infty dfrac ({(-1))^n+1}(2n+1)C.sum _(n=1)^infty dfrac ({(-1))^n+1}(2n+1)D.sum _(n=1)^infty dfrac ({(-1))^n+1}(2n+1)

求幂级数 sum _(n=1)^infty n(n+1)(x)^n 的收敛域及和函数并求 sum _(n=1)^infty dfrac (n(n+1))({2)

求级数 sum _(n=1)^infty dfrac (1)(n(n+1)(n+2)) 的和.-|||-__

求级数sum _(n=1)^infty dfrac (1)(n(n+1)(n+2))的和。求级数的和。

A12.1.4 下列级数中,收敛的级数是 __-|||-(A) sum _(n=1)^infty =dfrac (-2)(n) (B) sum _(n=1)^i

) ,若级数 sum _(n=1)^infty (a)_(n),sum _(n=1)^infty (b)_(n) 收敛,则 sum _(n=1)^infty (

证明：级数sum _(n=1)^infty (sin dfrac (1)({n)^2})收敛。证明：级数收敛。

1.求下列幂级数的收敛域(或收敛圆):-|||-(1) sum _(n=1)^infty dfrac (1)({2)^n}(x)^2n-1;-|||-(2) s

13.设 sum _(i=1)^infty (a)_(n)=1, 则 sum _(n=1)^infty ((a)_(n)-2(a)_(n+1))= __

(4)下列级数中,条件收敛的级数为 () .-|||-(A) sum _(n=1)^infty ((dfrac {1+3i)(2))}^n (B) sum _(

18.-|||-在下列无穷级数中,收敛的级数是 ()-|||-A sum _(n=1)^infty (sqrt (n+1)-sqrt (n));-|||-B s