I．“精制”过程是将含有少量CO、CO₂、O₂和H₂S等杂质的原料气体通入含有氨水的醋酸亚铜二氨（化学式为Cu （NH₃）₂Ac）溶液，以获得纯净原料气．其中，吸收CO的反应为：

CO+Cu （NH₃）₂Ac+NH₃•H₂O⇌Cu （NH₃）₃COAc+H₂O△H＜0．

请从4a²，（x+y）²，1，9b²中，任选两式做差得到的一个式子进行因式分解是____ 

读短文，完成下面各题。

    Hello, my name is Li Ming. My birthday is June 9th. My mother's birthday is June 14th. My grandpa's birthday is June 23th.My grandpa is in America, my grandpa lives with my uncle Bill and aunt Mary in America, so I usually make an e-card to him for his birthday.

My grandma's birthday is in July, it is very hot and sunny in July, then when her birthday is coming, we often go swimming for her birthday.