解:(1)y=x/x(x-1)*(x-1)²/(x-1)(x+1)-2/(x+1) =1/(x+1)-2/(x+1) =-1/(x+1)=1/3∴x+1=-3,x=-4即x=-4时,y=1/3(2)(a+b)/x=(a+b)²/ab∵a+b≠0∴x=ab/(a+b)(3)去分母:x+2+k(x-2)=4∵增根x=-2∴x=-2是x+2+k(x-2)=4的根∴-4k=4∴k=-1