(lg2)^2+lg20xlg5
问题描述：
(lg2)^2+lg20xlg5
答
(lg2)^2+lg20*lg5=(lg2)^2+lg(2*10)*lg5
=(lg2)^2+(lg2+lg10)*lg5
=(lg2)^2+(lg2+1)*lg5
==(lg2)^2+lg2*lg5+lg5
=lg2*(lg2+lg5)+lg5
=lg2*lg10+lg5=lg2+lg5=lg(2*5)=lg10=1