设x=lg5,lg2=1-lg5=1-x2x+(1-x)^3(1+x)=2x+(1-x)^2(1-x^2)=2x+(x^2-2x+1)(1-x^2)=2x+x^2-x^4-2x+2x^3+1-x^2=-x^4+2x^3+1=x^3(2-x)+1=(lg5)^3*lg20+1好像只能化到这了,不知道了.