（1）x+y=5 xy=6
(x+y)^2=x^2+y^2+2xy =25
x^2+y^2=25-12=13
(2)2a^2-2ab+b^2+4a+4
=(a-b)^2+(a+2)^2=0
a=b a=-2 b=-2
所以a^2b+ab^2=-8-8=-16
(3)a^2+(m-3)a+4 =(a+2)^2 或(a-2)^2
所以m-3=4 m=7 或m-3=-4 m=-1
选C
(4)8a^3 b^m /(28a^n *b^n) =2b^2/ 7
2a^3 b^m /(7 a^n*b^n) =2b^2/7
a^3 b^m/(a^n*b^n) =b^2
所以n=3 m-n=2 m=5
(5)2a^2+2a+2009=2(a^2+a)+2009=2009
(6)x-1/x =1
(x-1/x)^2=x^2+1/x^2 -2 =1
所以x^2+1/x^2 =3
二:
(1)-2a^3 b^2 +8a^2 b^2 -8ab^2 =-2ab^2(a^2-4a+4) =-2ab^2 *(a-2)^2
(2)a^4 -8a^2b^2 +166^4 =? 是不是a^4-8a^2 b^2 +16 b^4 =(a^2-4b^2)^2
=(a-2b)^2 *(a+2b)^2
三:
[(xy+2)(xy-2)-2x^2y^2+4] /(xy)
=[x^2 y^2 -4 -2x^2y^2+4]/(xy)
=[-x^2y^2]/(xy)
=-xy
=-10*1/25
=-2/5