It is known that A. B belongs to real number r. compare a ^ 4 + B ^ 4 with (a ^ 3) B + (b ^ 3) a?

It is known that A. B belongs to real number r. compare a ^ 4 + B ^ 4 with (a ^ 3) B + (b ^ 3) a?

A ^ 4 + B ^ 4-A ^ 3b-ab ^ 3 = a ^ 3 (a-b) - B ^ 3 (a-b) = (a ^ 3-B ^ 3) (a-b) = (a-b) ^ 2 (a ^ 2 + B ^ 2 + AB) greater than or equal to 0
So the fourth power of a + the fourth power of B is greater than or equal to the third power of a and the third power of B + ab