利用公式lga^b=blga知:lg25=2lg5, lg9=2lg3, lg2倍根号2=(3/2)*lg2 log2^25*log3^2倍根号2*log5^9 (利用loga^b=lga/lgb,化成同底形式)=[(lg25)/lg2]*[(lg2倍根号2)/lg3]*lg9/lg5(分母与分母乘,分子与分子乘)=[2lg5*(3/2)lg2*2lg3]/[lg2*lg3*lg5] =2*(3/2)*2=6