Function with a parameter.

[Guest]

f(x)=x*x-4x+1
y=mx+3/4

When y crosses f at the points A and B, we name I the middle point of (AB)
When m varies, there is a function formed by the succession of the points I.

Find this function

[somi]

in the binomial expansion of (1+1/3 x)^n , the coefficients of the fourth and fifth term are equal. Find the value of n.



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somi