先化简再求值：x-1/x²-9÷（x/x-3-5x-1/x²-9）,其中x=5.

题目

先化简再求值：x-1/x²-9÷（x/x-3-5x-1/x²-9）,其中x=5.

答案

x-1/x²-9÷（x/x-3-5x-1/x²-9）
=(x-1)/(x+3)(x-3) ÷ (x²+3x-5x+1)/(x+3)(x-3)
=(x-1)/(x-1)²
=1/(x-1)
=1/(5-1)
=1/4