n4na1+…+al na 2 十∴十 nim Ina,t lna2+…+ln 2 n 2 →li +a2+…+an n2 2 1 1 1 1 1 1 1 1 1 ln ln 1 lim x x a a a a a a n n x n x x n x x − −        + + + + = →   n a a a n n ln 1 + ln 2 + + ln =   ln( ) = a1a2 an x x n x x x n a a a           + + +  → 1 1 2 1 1 lim  ln( ) a1a2 an e  = = a1a2 an