(1)(m-n)^2*(n-m)^5*(m-n)^5
=(m-n)^2*[-(m-n)^5]*(m-n)^5
=-(m-n)^(2+5+5)
=-(m-n)^12
(2)(-x)^2*x^3+2x^3*(-x）^2-x*x^4
=x^2*x^3+2x^3*x^2-x^5
=x^5+2x^5-x^5
=2x^5