Question

已知a+b=5,ab=6,求二分之一a×b的三次方+a×b的三次方

Answer 1

a+b=5 ab=6

a=b/6

b/6+b=6

b+6b=36

7b=36

b=7/36

1/2ab^3+ab^3

=（1/2ab+ab）*b^2

=（1/2*6+6）*7/36

=9*7/36

=7/4