(a²-4)/(a-3)×(1-1/a-2)-a+1
=(a-2)(a+2)/(a-3)×(a-2-1)/(a-2)-a+1
=(a-2)(a+2)/(a-3)×(a-3)/(a-2)-a+1
=a+2-a+1
=3
∵(a²-4)/(a-3)×(1-1/a-2)-a+1=3
∴a只要任意取一个使原式有意义的值代入,原分式的值都等于3
(a²-4)/(a-3)×(1-1/a-2)-a+1
=(a-2)(a+2)/(a-3)×(a-2-1)/(a-2)-a+1
=(a-2)(a+2)/(a-3)×(a-3)/(a-2)-a+1
=a+2-a+1
=3
∵(a²-4)/(a-3)×(1-1/a-2)-a+1=3
∴a只要任意取一个使原式有意义的值代入,原分式的值都等于3