4m^4-1/2m
=1/2m(8m³-1)
=1/2m(2m-1)(4m²+2m+1)
2a+16ab^2
=2a(1+8b²)
（a-b+4）（a^2-2ab+b^2-4a+4b+16）
=[(a-b)+4][(a-b)²-4(a-b)+4²]
=(a-b)³+4³
=a³-3a²b+3ab²-b³+64