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
+a2b2+1 2a3b
的值为______. 1 2ab3
答
原式=
+a2b2
b2+a2
2a3b3
=
+(ab)2.(a+b)2−2ab 2(ab)3
∵a+b=3,ab=2,
∴原式=
+4
32−2×2 2×23
=
.69 16
故答案为:
.69 16