初二计算题化简因式分解和分式的题,求化简

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原式=x-x÷{(x+y)(x-y) / (x+y)(x²-xy+y²) [(xy-x²-y²) / y × xy / (y-x)]}
=x-x÷{(x-y) / (x²-xy+y²) × [-(x²-xy+y²)] / y × xy / [-(x-y)]
=x-x÷x
=x-1