已知a+b=3,ab=2,则1/2a3b+a2b2+1/2ab3的值为_.

问题描述:

已知a+b=3,ab=2,则

1
2a3b
+a2b2+
1
2ab3
的值为______.

原式=

b2+a2
2a3b3
+a2b2
=
(a+b)2−2ab
2(ab)3
+(ab)2
∵a+b=3,ab=2,
∴原式=
32−2×2
2×23
+4
=
69
16

故答案为:
69
16