a方=2ab+9b方 a=(根号5+1)b
lg(a方+ab-6b方)-lg(a方+4ab+15b方)
=lg((a方+ab-6b方)/(a方+4ab+15b方))
=lg(3ab+3b方)/(6ab+24b方)
=lg0.5*(a+b)/(a+3b)
再将a=(根号5+1)b代入
(答案似乎不是很方便)
a方=2ab+9b方 a=(根号5+1)b
lg(a方+ab-6b方)-lg(a方+4ab+15b方)
=lg((a方+ab-6b方)/(a方+4ab+15b方))
=lg(3ab+3b方)/(6ab+24b方)
=lg0.5*(a+b)/(a+3b)
再将a=(根号5+1)b代入
(答案似乎不是很方便)