a^2/b+b^2/a-(a+b)
=(a^3+b^3-a^2b-ab^2)/ab
=[(a+b)(a^2-ab+b^2)-ab(a+b)]/ab
=(a+b)(a^2-2ab+b^2)/ab
=(a+b)(a-b)^2/ab
a>0,b>0所以a+b>0,ab>0
a不等于b ,所以(a-b)^2>0
所以(a+b)(a-b)^2/ab>0
所以a^2/b+b^2/a>a+
a^2/b+b^2/a-(a+b)
=(a^3+b^3-a^2b-ab^2)/ab
=[(a+b)(a^2-ab+b^2)-ab(a+b)]/ab
=(a+b)(a^2-2ab+b^2)/ab
=(a+b)(a-b)^2/ab
a>0,b>0所以a+b>0,ab>0
a不等于b ,所以(a-b)^2>0
所以(a+b)(a-b)^2/ab>0
所以a^2/b+b^2/a>a+