解最简公分母2(x+y)²,∴(x-y)/(2x+2y)=(x+y)(x-y)/2(x+y)²=(x²-y²)/2(x+y)²xy/(x+y)²=2xy/2(x+y)²最简公分母4m²-9=(2m+3)(2m-3)∴2mn/(4m²-9)不变(2m-3)/(2m+3)=(2m-3...