Question

先化简，再求值：，其中x=﹣1．                  

Answer 1

【考点】分式的化简求值．                                                                     

【专题】计算题；压轴题．                                                                     

【分析】这是个分式除法与减法混合运算题，运算顺序是先乘除后加减，减法时要注意把各分母先因式分解，确定最简公分母进行通分；做除法时要注意先把除法运算转化为乘法运算，而做乘法运算时要注意先把分子、分母能因式分解的先分解，然后约分，最后代值进行计算．                                                       

【解答】解：原式=                         

=                                                                            

=                                                                           

=，                                                                                   

当x=﹣1时，原式=．                                         

【点评】本题主要考查分式的化简求值，式子化到最简是解题的关键．