Question

已知x=2，y=5。求1-(x-y/x-2y)÷(x²-y²/x²-4xy+4y²)

详细的化简过程，谢谢，

Answer 1

解:原式=1-(x-y/x-2y)÷((x+y)(x-y)/(x-2y)²)
=1-(x-y/x-2y)×((x-2y)²/(x+y)(x-y))
=1-(x-2y)/(x+y)
=(x+y)/(x+y)-(x-2y)/(x+y)
=((x+y)-(x-2y))/(x+y)
=(x+y-x+2y)/(x+y)
=3y/(x+y)
当x=2，y=5时，
原式=(3×5)/(2+5)
=15/7
化简过程中“/”都表示分数线