√2/2-√3/2-3√2/4+9√3/4=-√2/4+11√3/4 √ 27=3√3
1/2(根号2+根号3)-3/4(根号2-根号27)=1/2(根号2+根号3)-3/4(根号2-3根号3)=1/2*根号2+1/2*根号3-3/4*根号2+3/4*3根号3= -1/4*根号2+5/4*根号3
