计算：①2m²-m(2m-5n)-n(5m-n)②(3x-y)²-(3x+y)²-2xy③

①2m²-m(2m-5n)-n(5m-n)=2m²-2m²+5mn-5mn+n²=n²。②(3x-y)²-(3x+y)²-2xy=9x²-6xy+y²-(9x²+6xy+y²)-2xy=-6xy-6xy-2xy=-14xy。③(m+1)(m+2)(m-1)(m-2)=(m+1)(m-1)(m+2)(m-2)=(m²-1)(m²-4)=m的4次幂 - 5m² +4。④(x+1)²(x²+1)²(x-1)² =(x+1)²(x-1)²(x²+1)² =(x²-1)²(x²+1)² = (x的4次幂-1)²=x的8次幂 - 2*x的4次幂 +1。因式分① 3分之4x²y³-9分之2x³y =9分之2*x²y*(6y²- x²) =9分之2*x²y*(根号6*y +x) (根号6*y -x)。②(x²+4)²-16x² =[(x²+4)+4x]²[(x²+4)-4x]² =(x²+4x+4)²(x²-4x+4)² =(x+2)的4次幂*(x-2)的4次幂。③16x的四次方-8x²y²+y的四次方 =(4x²-y²)²=(2x+y)²(2x-y)²。④-5a³+5a=-5a(a²-1)=-5a(a+1)(a-1)