Question

第九题，求详细解答步骤

Answer 1

a5*a（2n-5）=2^(2n)(n≥3)
a1*q^4 *
a1*q^(2n-6)=2^(2n)
a1^2*q^(2n-2)=2^(2n)
an=2^n
所以log2（a1）+log2（a2）+……+log2[a（2n-1）]
=log2（2^1）+log2（2^2）+……+log2[a（2n-1）]
=1+2+……+(2n-1)
=[(2n-1)*(1+2n-1)]/2
=n*(2n-1)