1.设等比数列通项：an=a1*q^(n-1),因此a4*a6=（a1）^2*q^8=a3*a7 所以 log3(a3)+log3(a7)=log3(a3*a7)=log3(9)=2 2.Sn=[n(n+2)/8+1-(1/2)^(n/2)]*[1+(-1)^n]/2 +{(n+1)(n+3)/8+1-(1/2)^[(n-1)/2]*[1-(-1)^n]/2第二题...