（根号24+根号216）/根号6
=(2√6+6√6)/√6
=2+6
=8
3倍根号18-1/2倍的根号32-7倍的根号1/8
=9√2-1/2×4√2-7×1/2×√2/2
=9√2-2√2-7√2/4
=7√2-7√2/4
=21√2/4