概念
分式乘法法則為:分式乘以分式,用分子的積做積的分子,分母的積做積的分母。即
![分式乘法法則](/img/9/f64/wZwpmL1YzN1ITM4MzM2EzM1UTM1QDN5MjM5ADMwAjMwUzLzMzL3czLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
分式乘法的注意事項
分式的乘除法法則與分數的乘除法法則類似,法則中的a,b,c,d可以代表數也可以代表整式。
分式乘除法的運算,歸根到底是乘法運算,由乘法法則,應先把分子、分母分別相乘,化成一個分式後再進行約分,但在實際演算時,這樣做有時顯得繁瑣,因此,可根據情況約分,再相乘。
分式的乘除運算,當分子和分母是多項式時,一般應先進行因式分解,再約分,把分子和分母中含有同一字母的多項式按降冪(或升冪)排列後,容易看出分子與分母的公因式,便於約分。
對於分式乘除法,如果只含同級乘除運算,而沒有附加條件(如括弧等),那么就應按照由左到右的順序進行計算如
![分式乘法法則](/img/8/c4b/wZwpmLzcDM4gDO4YTM2EzM1UTM1QDN5MjM5ADMwAjMwUzL2EzL0MzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
而
![分式乘法法則](/img/2/2db/wZwpmL0QjMyITNwUzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL1MzLxYzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![分式乘法法則](/img/6/a01/wZwpmLwEDM3YDN3EjM2EzM1UTM1QDN5MjM5ADMwAjMwUzLxIzLyUzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
則是錯誤的,這種錯誤是由於按照的順序計算造成的 。
例題解析
【例1】計算 :
![分式乘法法則](/img/1/ed1/wZwpmL3YTOxMDNzczM2EzM1UTM1QDN5MjM5ADMwAjMwUzL3MzLyczLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![分式乘法法則](/img/8/40b/wZwpmLxATOwYDM2QzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0MzLxgzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![分式乘法法則](/img/5/a03/wZwpmLwgjMxQjM0czM2EzM1UTM1QDN5MjM5ADMwAjMwUzL3MzL4IzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![分式乘法法則](/img/5/1be/wZwpmL0YTNyUjM2QzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0MzL0IzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![分式乘法法則](/img/2/994/wZwpmL3QDN5QTNxQTM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0EzLzQzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![分式乘法法則](/img/7/a5b/wZwpmL3UzM5ATNycTM2EzM1UTM1QDN5MjM5ADMwAjMwUzL3EzLwYzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
解:
![分式乘法法則](/img/0/c3d/wZwpmLyADO2YjNxEjM2EzM1UTM1QDN5MjM5ADMwAjMwUzLxIzL0IzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![分式乘法法則](/img/7/cf9/wZwpmL3gjMxYzM0QzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0MzLwczLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![分式乘法法則](/img/b/f64/wZwpmLyczM0MTM4QTM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0EzL2AzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![分式乘法法則](/img/6/d5b/wZwpmL1UzN1MDO2EDN2EzM1UTM1QDN5MjM5ADMwAjMwUzLxQzL2czLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![分式乘法法則](/img/3/790/wZwpmLwcDNzgzNyQzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL0MzL1UzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![分式乘法法則](/img/7/4ac/wZwpmL4MjM2QTMwUTM2EzM1UTM1QDN5MjM5ADMwAjMwUzL1EzLwIzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![分式乘法法則](/img/0/cbe/wZwpmL1ADNxQTM0YzM2EzM1UTM1QDN5MjM5ADMwAjMwUzL2MzL2EzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![分式乘法法則](/img/c/598/wZwpmLwEDOzcDNzIDN2EzM1UTM1QDN5MjM5ADMwAjMwUzLyQzLzczLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)