[(x^2+y^2)(a^2+b^2)+4abxy]^2-4[xy(a^2+b^2)+ab(x^2+y^2)]^2设x²+y²=m,a²+b²=n,xy=p,ab=q,则原式化为（nm+4pq)²-4(pn+qm)²=(nm+4pq+2pn+2qm)(nm+4pq-2pn-2qm)=[n(m+2p)+2q(m+2p)][n(...