Find the intervals in which `f(x)=(4x^2+1)/x` is increasing or decreasing.

Explanation

`f(x)=(4x^2+1)/x`

`f^'(x)=(x d/(dx)(4x^2+1)-(4x^2+1)d/(dx)x)/(x^2)`


`f^'(x)=(x(8x)-(4x^2+1))/(x^2)`


`f^'(x)=(4x^2-1)/(x^2)`


So,

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