* x1, ..., xn are real numbers

* w1, ..., wn are real numbers

* t is a scalar

What value minimizes f(t), when f(t) = Sumation (from i=0, to n) wi(t - xi)^2

This is a simple problem, the function is minimized when t = xi. But I wonder about the formal explanation

Besides, not sure about the implications of t being negative.