find the interval(s) where the following functions are increasing and decreasing.
f(x)= x/4 + 4/x
f ' (x) = 1/4 - 4/x^2
= 0 for a turning point (max/min)
1/4 = 4/x^2
x^2 = 16
x = ± 4
make a rough sketch to see that
the curve is increasing for x<-4 OR x>4
the curve is decreasing for -4 < x< 4 , x±0