计算：①2m²-m(2m-5n)-n(5m-n)②(3x-y)²-(3x+y)²-2xy③(m+1)(m+2)(m-1)(m-2)
④(x+1)²(x²+1)²(x-1)²
因式分解：①3分之4x²y³-9分之2x³y ②(x²+4)²-16x² ③16x的四次方-8x²y²+y的四次方 ④-5a³+5a