∵x²y²≤(x²+y²)²/4∴0≤(x²+y²)^(x²y²)≤(x²+y²)^[(x²+y²)²/4]∵lim(x->0,y->0){(x²+y²)^[(x²+y²)²/4]}=lim(t->...对数性质是：x=e^lnx(x>0)