Question

先化簡，再求值：，其中x=﹣1．                  

Answer 1

【考點】分式的化簡求值．                                                                     

【專題】計算題；壓軸題．                                                                     

【分析】這是個分式除法與減法混合運算題，運算順序是先乘除后加減，減法時要注意把各分母先因式分解，確定最簡公分母進行通分；做除法時要注意先把除法運算轉(zhuǎn)化為乘法運算，而做乘法運算時要注意先把分子、分母能因式分解的先分解，然后約分，最后代值進行計算．                                                       

【解答】解：原式=                         

=                                                                            

=                                                                           

=，                                                                                   

當x=﹣1時，原式=．                                         

【點評】本題主要考查分式的化簡求值，式子化到最簡是解題的關鍵．