分式有意义的条件是分母不为0,所以讨论分式问题时,必须注意这一点.另外,还应当注意隐含条件的充分挖掘,以得出符合题意的结论来.下面,结合例题进行说明.例1在什么条件下,下列分式的值是0?(1)(x-1)/x;(2)(5a-b)/(a+b).解析:(1)由x-1=0,所以x的值是1.这时分母不为0.所以符合题意的x的值是1. The conditional significance of the fractional formula is that the denominator is not zero, so we must pay attention to this when discussing the fractional problem. In addition, we should also pay attention to the full excavation of the implied conditions to arrive at the conclusion that is in line with the questioning. Example 1 Under what conditions, the value of the following fraction is 0? (1) (x-1) / x; (2) (5a-b) / (a ​​+ b) x-1 = 0, so the value of x is 1. Then the denominator is not 0. Therefore, the value of the x that meets the questions is 1.