（1-x+2分之1）除于x+2分之x的2次方-1=(1-x+1/2)/x+(x²-1)/2=(3/2-x)/x+(x²-1)/2=3/2x-1+x²/2-1/2=x²/2+3/2x-3/2x=2;原式=4/2+3/(2×2)-3/2=2+3/4-3/2=5/4;
