2022深圳九年级学英语周报答案

re going to get back可知, Billy Shelby相信正能量61. exploring/exploration 62. farther/further 6a writteh: 64, has remained 65. by 66.themselves67. widely 68 collection 69. when: 70.a

19解:(1)由a2+a12=30及S8=80,a1+d+11d=30,8×78a1+2即/Q1+6d(3分)2a1+7d=20,解得/(=3,所以an=2n+1(5分)(2)由(1)得W+1)(2n+3)=2(2n+12n+3)(6分)所以Tn=b1+b2+…+b=2[(3-5)++(2n+12n+3)=2(3-2n+33(2n+(9分)+所以Tn+3(2n+5)(10分)所以Tn-1T3(2n+53(2n+3(2n+5)(2n+3)所以{Tn}为递增数列所以Tn≥T1=1又T所以T,∈(12分)

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