最佳答案:{a}是等比数列,an>0有An=A1*Q^(N-1)A1*Q^3*A1*Q^5+2*A1*Q^4*A1*Q^6+A1*Q^5*A1*Q^7=36A1^2*Q^
最佳答案:因为{an}是等比数列,故:a2a4=(a3)²,a4a6=(a5)²,故:a2a4+2a3a5+a4a6=(a3)²+2a3a5+(a5)²=36,即:(a3
最佳答案:1:10X-25.5=36 X=6.152:5.6X+4.2=8.4 X=0.753:油X 桶YX+Y=26.3X/2+Y=14X=24.6Y=1.7