Ethem S. answered 10/09/19
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You need to find the value of x that minimizes the cost function.
c(x) = 2300-50x+0.2x2
The minimum is at the point where slope is 0. The slope is the first derivative of c(x) with respect to x.
d c(x) / dx = -50+0.4x (derivative of constant 2300 is 0. derivative of -50x is -50. Derivative of 0.2x2 is 0.2*2*x)
Set the slope to 0,
-50+0.4x = 0
0.4x = 50
x = 125