解a²-1/25b²=a²-(1/5b)²=(a-1/5b)(a+1/5b)m²(x-y)+n²(y-x)=m²(x-y)-n²(x-y)=(x-y)(m²-n²)=(x-y)(m+n)(m-n)16(x+y)²-25(x-y)²=[4(x+y)]²-[5(x-y)]...