Question

化简：1-

x+y

x-3y

÷

x2-y2

x2-6xy+9y2

=

 

．

Answer 1

分析：把第二个分式的分子分母先因式分解，再把除法统一成乘法化简，最后算减法．

解答：解：1-

x+y

x-3y

÷

x2-y2

x2-6xy+9y2

=1-

x+y

x-3y

•

(x-3y)2

(x+y)(x-y)

=1-

x-3y

x-y

=

x-y-x+3y

x-y

=

2y

x-y

．

点评：此题运算顺序：先除后减，用到了分解因式、约分、合并同类项等知识点．