Integer rounding or integer?

2. Regarding the symmetry of x= 1, let's take X =- 1 and X = 3, and then take X = 0 and X = 2, and then bring them in. Both can get two values of a, and take the same two.

3. If the loss of each block is 10%, then let's set x blocks. If it is weakened to the original 1/3, the loss will be 2/3, so the x power of 0. 1 is 2/3, and then the calculator will work out.

4, f(-x)=f(x), it is an even function, the solution is symmetric about x=0, the symmetric sum is 0, and another solution must be x=0, then the sum of these 2009 real numbers is 0.

5.f(x)=x- 1/x, bring in f(mx)+mf(x) to get MX-1/(MX)+MX-m/x; 0，2mx 2- 1/m-m

6.f(x+4)≤f(x)+4 and f(x+2)≥f(x)+2,

Replace x in f(x+4)≤f(x)+4 with x-2 to get f(x+2)≤f(x-2)+4, then f(x)+2≤f(x+2)≤f(x-2)+4,

Let x = 1, f (1)+2 ≤ f (3) ≤ f (-1)+4, then f( 1)≤2,

Let x=3, f(3)+2≤f(3+2)≤f(3-2)+4, then f( 1)≥2, then f( 1)=2.

Continue to use this value method.