已知m，n是实数，且当x>2015时，mx－2＋nx＋2=5x＋2x2－4恒成立，则m²－n²=（）.

W: Is Aunt Mary in? I’ve got something important to tell her.M: Sorry, mother has gone shopping. She won’t be back until lunch time.Q: What is the relationship between the two speakers?（）

A．Father and daughter.
B．Uncle and niece.
C．Aunt and nephew.
D．Cousins.

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已知a+b+c=1,ab+c+bc+a+ca+b=3.则1 (b+c)+1 (c+a)+1 (a+b)=（）. 点击查看答案