16[(x+y)²]-25[(x-y)²] 　　=[4(x+y)+5(x-y)][4(x+y)-5(x-y)]　　=(9x-y)(9y-x)[(5m²+3n²)²]-[(3m²+5n²)²]　　=[(5m²+3n²)+(3m²+5n²)][(5m²+3n&#...