∵x - 2y=3∴2y=x - 3则原式=[(3x+x-3)(3x-x+3) - (x+x-3)]÷(x/3)=[(4x-3)(2x+3) - (2x-3)]÷(x/3)=(8x² + 6x - 9 - 2x + 3)÷(x/3)=(8x² + 4x - 6)×(3/x)=24x + 12 - 18/x
你把所有的y换成x
30/x=40/y
