1.log(2)根号18+1/2log(2)56-log(2)3根号7=log(2).sqrt(18)+log(2).sqtr(56)-log(2).sqrt(9*7)=log(2).(sqrt(18)*sqrt(56)/sqrt(63))=log(2).sqrt(16)=log(2).4=2
2.lg以(5)为底2的对数+2/3lg8+lg5*lg20+lg2=log5(2)+2lg2+(1-lg2)(3-lg2)+lg2=lg2/(1-lg2)+2lg2+3-4lg2+(lg2)^2+lg2=lg2/(1-lg2)+(lg2).^2-lg2+3
3.2log以（3）为底2的对数-log(以3)为底32/9的对数+log以（3）为底8的对
log3=log(3).4-log(3).(32/9)+log(3).8=log(3).(4*9*8/32)=log(3).9=2
4.（log以（5）为底根号2的对数*log以7为底9的对数）/（log以（5）为底1/3的对数*log以7为底4的立方根的对数=(1/2log(5).2×2log(7).3)/(-log(5).3×6log(7).2)=-1/6*log(3).2/log(2).3=-1/6
