原式=1+1/2-(1+3/4)-(1+1/4)+(4+1/2)
=1-1-1+4+1/2-3/4-1/4+1/2
=3+1-1
=3
或
原式=(1+1/2+4+1/2)-(1+3/4+1+1/4)
=6-3