Question Number 100539 by Dwaipayan Shikari last updated on 27/Jun/20

(−1)^n Σ_(n=1) ^∞ (3^n /n)

Commented bymaths mind last updated on 27/Jun/20

Σ_(n≥1) (−1)^n (3^n /n) this diverge

Commented byabdomathmax last updated on 27/Jun/20

S =Σ_(n=1) ^∞ u_n with u_n =(((−3)^n )/n) we have ∣(u_(n+1) /u_n )∣ =(3^(n+1) /(n+1))×(n/3^n ) =((3n)/(n+1)) →3 >1 ⇒Σ u_n diverges