首先,有这么一个规律
lg0.2=lg5^(-1)=-lg5
对数的底数也满足这个规律
所以呢
log0.2/log0.5=log5/log2
log2/log0.2=-log2/log5
log0.5/log5=-log2/log5
（log5/log2+log0.2/log0.5)(log2/log0.2+log0.5/log5)
=2log5/log2 * (-) 2log2/log5
=-4