sn=2an-1s1=2a1-1=a1,a1=1s(n-1)=2a(n-1)-1an=2an-1-2a(n-1)+1an=2a(n-1)an=a1*2^(n-1)=2^(n-1)b(k+1)=ak+bk=2^(k-1)+bkb(k+1)-bk=2^(k-1) bk-b(k-1)=2^(k-2)b(k-1)-b(k-2)=2^(k-3)……b4-b3=2^2b3-b2=2^1b2-b1=2^0...