令lg2=a
lg5=b
则a+b=lg10=1
lg25=lg5^2=2lg5=2b
lg50=lg5+lg10=b+1
lg500=lg5+lg100=b+2
所以原式=2b+(b+1)+a(b+2)+a^2
=3b+1+ab+2a+a^2
=b+1+(ab+a^2)+(2a+2b)
=b+1+a(a+b)+2
=b+3+a
=1+3=4