1.log3 3/log27 64
=log27 27/log27 64
=27/64
2.log8 9 .log3 2 (是乘吗?）
=(lg9/lg8)(lg2/lg3)
=(2lg3/3lg2)(lg2/lg3)
=2/3
3.log3 (lnx)=1 (因为logπ 1=0)
ln x=3 (因为log3 3=1)
log e x=3
x=e^3
4.lg(x-y)+lg(x+2y)=lg2+lgx+lgy
lg((x-y)(x+2y))=lg(2.x.y)
x^2+2xy-xy-2y^2=2xy
x^2-xy-2y^2=0
(x-2y)(x+y)=0
用同步方程,x=0,y=0
不过0/0不合理啊...是不是问题出错了?
5.真挺难的.抱歉!
我尽力了!