①设T(n)=(1/2)*a(1)+(1/2^2)*a(2)+……+(1/2^n)*a(n),则据题意有T(n)=5+2n;
②)(1/2^n)*a(n)=T(n)-T(n-1)=2,所以 a(n)=2^(n+1);
③S(n)=4+8+16+……+2^(n+1)=2^(n+2)-4
①设T(n)=(1/2)*a(1)+(1/2^2)*a(2)+……+(1/2^n)*a(n),则据题意有T(n)=5+2n;
②)(1/2^n)*a(n)=T(n)-T(n-1)=2,所以 a(n)=2^(n+1);
③S(n)=4+8+16+……+2^(n+1)=2^(n+2)-4