calculus
posted by H .
The value of c for which f(x) = x + c/x has a local minimum at x= 3 is
(a) 9
(b)  6
(c) 3
(d) 6
(e) 9

df/dx = 1  c/x^2 = 0
If the minimum is at x = 3, then
c/x^2 = c/9 = 1
c = 9
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