（根号12-根号二分之一-2倍根号3分之1）-根号8分之1+根号18
=[√12-√(1/2)-2√(1/3)]-√(1/8)+√18
=[2√3-√2/2-2√3/3]-√2/4+3√2
=2√3-√2/2-2√3/3-√2/4+3√2
=2√3-2√3/3+3√2-√2/2-√2/4
=4√3/3+9√2/4
=1.732*4/3+9/4*1.4.4
=2.3093+3.1815
=5.4908