1.原式=(3a+2b+a+b-b+a)/5a²b=(5a+2b)/3a²b
2.原式=(m+2n+n+2m)/n-m=3(m+n)/(n-m)
3.原式=(a-3)/(a-3)(a+3)+6/(a-3)(a+3)=(a-3+6)/(a-3)(a+3)=(a+3)/(a-3)(a+3)=1/(a-3)
4.原式=(x+3)/(x+3)(x-3)+(0.5-0.5x)(x-3)/(x+3)(x-3)-6/(x+3)(x-3)=-(x-3)(x-3)/2(x+3)(x-3)=-(x-3)/2(x+3)