Reward the next question, (1)a 1=a2-d=8-d and S6 = na1+(n-1) d/2 = 66, where n=6 is the solution; D=2 a 1=6, so an=2n+4.

(2)bn = 2/(n+ 1)(2n+4)= 1/(n+ 1)(n+2)= 1/n+ 1- 1/n+2

Then TN = b1+B2+''''+BN =1/2-1/3-1/4+'''+65438+.

Then when n= 10, t10 =1/2-12 = 5/12.