This problem is quiet similar with the lecture example, except for the [-a,a] instead of [0,a] fxi(xi;a)=1/(2a) if -a=<xi=<a, i.e |xi|<=a; and =0 if |xi|>a therefore, if any |xi|>a, the whole thing is zero for a>=max|xi| fx1..xn(x1..xn;a)=(1/2a)^n, is an decreasing function
when a=max|xi|, function is max.
