1/2lg32/49-4/3lg根号8+lg根号245
=1/2(5lg2-2lg7)-4/3(3/2lg2)+1/2(lg5+2lg7)
=5/2lg2-lg7-2lg2+1/2lg5+lg7
=1/2lg2+1/2lg5
=1/2(lg2+lg5)
=1/2lg10
=1/2