lg5²+2/3lg8+lg5*lg20+lg²2
=lg25+lg 8^(2/3)+lg5*lg20+lg²2
=lg25+lg4+lg5*(lg10+lg2)+lg²2
=lg(25*4)+lg5+lg5*lg2+lg²2
=2+lg5+lg2(lg5+lg2)
=2+lg5+lg2*lg10
=2+lg5+lg2
=2+lg10
=3
lg5²+2/3lg8+lg5*lg20+lg²2
=lg25+lg 8^(2/3)+lg5*lg20+lg²2
=lg25+lg4+lg5*(lg10+lg2)+lg²2
=lg(25*4)+lg5+lg5*lg2+lg²2
=2+lg5+lg2(lg5+lg2)
=2+lg5+lg2*lg10
=2+lg5+lg2
=2+lg10
=3