1.根号18+根号72-根号32
=√18+√72-√32
=3√2+6√2-4√2
=√2(3+6-4)
=5√2 .
2.根号4x-根号9x
=√4x-√9x
=(2-3)x
=-x .
3.根号27-根号12+根号4/3
=3√3-2√3+2/3*√3
=(3-2+2/3)√3
=5/3*√3 .
4.（根号12-根号8）/（根号48-根号32）
=(√12-√8)/(√48-√32)
=2(√3-√2)/[4(√3-√2)]
=1/2
5.根号5-根号6-根号20+根号2/3+根号9/5
=√5-√6-√20+√(2/3)+√(9/5)
=√5-√6-2√5+√6/3+3√5/5
=√5(1-2+3/5)-(1-1/3)√6
=-2/5√5-2/3√6 .
6.根号12-根号0.5-2根号1/3-根号1/8+根号18
=2√3-√2/2-2/3√3-√2/4+3√2
=√3(2-2)-√2(1/2+1/4-3)
=9/4√2 .