Let f(x) be a continuously differentiable function on the interval (0, ∞) such that f ( 1 ) = 2 and lim t → x t 10 f ( x ) − x 10 f ( t ) t 9 − x 9 = 1
for each x > 0. Then, for all x > 0, f(x) is equal to
31 11 x − 9 11 x 10
9 11 x + 13 11 x 10
− 9 11 x + 31 11 x 10
13 11 x + 9 11 x 10
