Question

计算（x-y+

4xy

x-y

）（x+y-

4xy

x+y

）的结果正确的是（　　）

A．y2-x2

B．x2-y2

C．x2-4y2

D．4x2-y2

Answer 1

（x-y+

4xy

x-y

）（x+y-

4xy

x+y

）=[

(x-y)2+4xy

x-y

][

(x+y)2-4xy

x+y

]=

(x+y)2

x-y

•

(x-y)2

x+y

=x²-y²．
故选B．