If f (x) has continuous derivatives in [1, + ∞), and satisfies X-1 + X ∫ (upper limit x, lower limit 1) f (T) DT = (x + 1) ∫ (upper limit x, lower limit 1) TF (T) DT, find f (x) The answer is f (x) = x ^ (- 3) * e ^ (1-1 / x),

If f (x) has continuous derivatives in [1, + ∞), and satisfies X-1 + X ∫ (upper limit x, lower limit 1) f (T) DT = (x + 1) ∫ (upper limit x, lower limit 1) TF (T) DT, find f (x) The answer is f (x) = x ^ (- 3) * e ^ (1-1 / x),

The original equation can be reduced to: X-1 = x * ([1, x] ∫ t * f (T) DT) + [1, x] ∫ t * f (T) DT - x * ([1, x] ∫ f (T) DT) = x * ([1, x] ∫ t-1) * f (T) DT) + [1, x] ∫ t * f (T) DT -- - (1) let F1 (T) = ∫ (t-1) * f (T) DT, F2 (T) = ∫ t * f (T) DT, then: F1 '(T) = (t-1) * f (...)