原式=√(1/2)-√18-2√(1/3)+√8+(1/5)√75=√(2/4)-√(9×2)-2√(3/9)+√(4×2)+(1/5)√(25×3)=√2/√4-√9×√2-2√3/√9+√4×√2+(1/5)×√25×√3=(√2)/2-3√2-(2√3)/3+2√2+√3=[(√2)/2-3√2+2√2]+[-(2√3)/3 +√3]=-(√2)/2 +(√3)/3
