?a?b??a5?b5??a?ab?ab?b??a?b??2ab?ab?a?4?ab?a?b?6556332332224?b4?
?4(2)因为
?a?b?3?a3?3a2b?3ab2?b3?2?3ab?a+b??2+33?a+b?42?a+b??2?3?a+b?43
所以?a+b??8,因此a+b≤2.
11
?a?b??a5?b5??a?ab?ab?b??a?b??2ab?ab?a?4?ab?a?b?6556332332224?b4?
?4(2)因为
?a?b?3?a3?3a2b?3ab2?b3?2?3ab?a+b??2+33?a+b?42?a+b??2?3?a+b?43
所以?a+b??8,因此a+b≤2.
11