One: x belongs to (3,5), then x+ 1 belongs to (4,6) function f (x) =1/(x+1in) (4,6) is a monotonically decreasing function, so F (X) Max = F (3.

Second, the domain of f(x) is any number of r, x 1, x2, x 1 >; X2, then f(x1)-f (x2) = a-1(1+2x1)-[a-1(1+2x2)].