先化简,再求值:(1+1/x-2)除x方-2x+1/x方-4,其中x=5

题目

先化简,再求值:(1+1/x-2)除x方-2x+1/x方-4,其中x=5

答案

(1+1/(X-2))÷(X^2-2X+1)/(X^2-4)
=(X-1)/(X-2)*(X+2)(X-2)/(X-1)^2
=(X+2)/(X-1)
当X=5时
原式=7/4