2. According to the question, 1

3、2x？ -4xy+4y？ -6x+9=(x？ -4xy+4y？ )+(x？ -6x+9)=(x-2y)？ +(x-3)？ =0, then x=3, y= 1.5, root number 18xy=9.

4 、( x- 10)(x-a)+ 1=x？ -(a+10) x+(10a+1) is completely flat, so 10a+ 1=(a/2+5)? ，a=-4，20

5 、( b-c)？ =(b+c)？ -4bc=64-4(a？ - 12a+52)=-4(a-6)？ . Because (b-c)? & gt=0, then a-6=0 and a=6, then the circumference of triangle abc is 6+8= 14.

6.abc=2008=2*2*2*25 1。 Because 25 1 is a prime number, one of abc's three numbers must be 25 1. Suppose a=25 1, then bc=8. Bc is a positive integer, then b+c is 9 or 6, and the minimum value of a+b+c is 257.

7, m=-a-402 1, n=a-4025, then m-n=4-2a, when a < 2, m>n, when a=2, m=n, when a >; At 2 o'clock, m < n

8 、( x+y)？ =(x-y)？ -4xy=64-4(z？ + 16)=-4z？ , so (x+y)? +4z？ =0, that is, X+Y = 0 and Z = 0, so x+y+z=0.

9. to (a 1+ 1)? +(a2+ 1)？ +……+(a50+ 1)？ =0, then A 1 = A2 = …+A50 =- 1, then A 1+A2+…+A50 can't be equal to 9, then (a1+kloc-0/)? +(a2+ 1)？ +……+(a50+ 1)？ The number of zeros is 0.

10, let a=x? -Really? , then a 1=x 1? -y 1？ ，a2=x2？ -y2？ , and so on, a2008=x2008? -In 2008?

Let y=x-z, then a=x? -Really? =x？ -(x-z)？ =2xz-z？ , it can be concluded that when z= 1, the value of a is the smallest. From the problem, x & gt=2, then x2008=2009, then a2008=40 17.