It is known that y = f (x) is an even function. When x > 0, f (x) = x + A / X (a > 0). When x is greater than or equal to - 3 and less than or equal to - 1, n ≤ f (x) ≤ m is constant 1) If a = 1, find the minimum of m-n 2) Finding the minimum value g (a) of M-N 3) When a > 16, is there K belonging to (1,2)], such that the inequality f (k-cosx) is greater than or equal to f (k ^ 2 - (cosx) ^ 2) belongs to R constant for any x? If so, find out the range of real number k; if not, explain the reason

It is known that y = f (x) is an even function. When x > 0, f (x) = x + A / X (a > 0). When x is greater than or equal to - 3 and less than or equal to - 1, n ≤ f (x) ≤ m is constant 1) If a = 1, find the minimum of m-n 2) Finding the minimum value g (a) of M-N 3) When a > 16, is there K belonging to (1,2)], such that the inequality f (k-cosx) is greater than or equal to f (k ^ 2 - (cosx) ^ 2) belongs to R constant for any x? If so, find out the range of real number k; if not, explain the reason

The first question is that we should guide the people in the area again! Min is 4 / 3! I don't know if it's right! I haven't touched it for two months! But I want to guide it! I hope it can help you a little!