化简(x^2-2x)/(x^2-1)除以[(2x-1)/(x+1)-x+1] 再选一个合适的值代入求值_数学解答

化简(x^2-2x)/(x^2-1)除以[(2x-1)/(x+1)-x+1] 再选一个合适的值代入求值

人气：150 ℃　时间：2020-09-01 06:57:18

解答

原式=(x²-2x)/(x+1)(x-1)÷[(2x-1)/(x+1)-(x-1)]
=(x²-2x)/(x+1)(x-1)÷[(2x-1-x²+1)/(x+1)]
=(x²-2x)/(x+1)(x-1)×[-(x+1)/(x²-2x)
=-1/(x-1)
令x=5
原式=-1/(5-1)
=-1/4