①x^2*(x-y)+y^2*(y-x)
=(x-y)(x^2-y^2)
=(x+y)*(x-y)^2

②25(m+n)^2-9n^2
=[5(m+n))^2-(3n)^2
=(5m+5n+3n)*(5m+5n-3n)
=(5m+8n)*(5m+2n)