【a+1分之3-a+1】除以 a+1分之a平方-4a+4 并从0,-1,2中选一个合适的数作为a的值代入求值.

[(3-a+1)/(a+1)]/[(a方-4a+4)/(a+1)]
=[(3-a+1)/(a+1)]/[(a-2)方/(a+1)]
=[(3-a+1)/(a+1)]*[(a+1)/(a-2)方]
=(3-a+1)*[1/(a-2)方]
=(3-0+1)*[1/(0-2)方]
=4*(1/4)
=1
注:a+1和a-2作为分母都不能等于0,所以a不能取-1和2,只能取0