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Kunming No.1 Middle School 20 16 Senior High School New Curriculum Standard Junior High School Mathematics Answers
n= 1,s 1 = a 1 = 2a 1- 1/2,a 1= 1/2

n≥2,an = Sn-S(n- 1)=(2an- 1/2)-(2a(n- 1)- 1/2)= 2an-2a(n- 1)

an=2a(n- 1)

an/a(n- 1)= 2

Therefore, the sequence {an} is a geometric series with the first term a 1= 1/2 and the common ratio of 2, and an =1/2 * 2 (n-1) = 2 (n ≥/kloc-)

bn=log? 2^n=n

Tn=b 1+b2+…+bn

= 1+2+…+n

=n(n+ 1)/2