已知等比数列{An}满足An>0,n=1,2,……,且A5*A(2n-5)=2的2n次方(n≥3),则当n≥1时,
问题描述:
已知等比数列{An}满足An>0,n=1,2,……,且A5*A(2n-5)=2的2n次方(n≥3),则当n≥1时,
则当n≥1时,log2A1+log2A3+……+log2A(2n-1)=?请附上解题过程,
答
a5 * a(2n-5) = 2^2n = a1 * a(2n-1) = a1a1q^(2n-2);
因为an > 0;所以:;a1q^(n-1) = an = 2^n;log2 an = n;原式 = 1 + 3 +.+ 2n-1;= n^2