Find the first four terms and the (n + 1 )st term of the series whose nith term is as follows: 1. ( - 1 )n - 1 X ( 2n ) ! 2. ( - 1 )n-1_2n- 1 n (n+ 2 ) 2n - 1 3. n (n+ 1 ) 4. en 5. -2 5n - 1 II. Find an nth term of the following series : 2 4 8 16 2) 3+4 +5+6+ O! . 1! 21 31 3) 1 -4+x2 x3 + ... 4! 7! 10! 4) 3 + 5 + 7 + 2+... 2! 3! 4! 5) 1 - 1+2- 2+