p2 - 1 =
p(p - 1)
(p - 1)(p - 1)
(p - 1)(p + 1)
(p + 1)(p + 1)
p2 - 1 = (p - 1)(p + 1)
limπ→∞ 1ρ+2ρ+3ρ+⋯+nρnρ+1= [AIEEE 2002]