If the function f (x) = x + radical (13-2tx), where t is a positive integer, the maximum value of the expression is a positive integer m, and the positive solution of M is 7 When t = 78, x = - 1 The root sign is 169 - 1 + 13 = 12 I know that. I want to help me see what's wrong with the following?

If the function f (x) = x + radical (13-2tx), where t is a positive integer, the maximum value of the expression is a positive integer m, and the positive solution of M is 7 When t = 78, x = - 1 The root sign is 169 - 1 + 13 = 12 I know that. I want to help me see what's wrong with the following?

① Derivation of the radical (T) - 2x / (T-13))
Let f (x) '= 0, that is, 1 - t / (radical (13-2tx)) = 0
x=(13-t^2)/(2t)
We know that when x = (13-t ^ 2) / (2t), f (x) gets the maximum, and f (x) is the maximum = (13 + T ^ 2) / (2t)
When x = 13 / 2T, f (13 / 2t) = 13 / 2T

If the maximum value of function f (x) = x + √ 13-2mx (m ∈ n *) is a positive integer m, then M = ■

13-2mx=1,9
2mx=12,4
mx=6,2
mx=6,f(x)=x+1=6/m+1=m-->m=3 ,f(x)=3
mx=2,f(x)=x+3=2/m+1=m-->m=2,f(x)=2
So m = 3