math
posted by Derek .
If y= (x^2+20)/(x4) Find all critical Numbers.
After get f' i got the answer 5/4. What did i do wrong or is that the critical number?

critical number: where y'=0 or y' undefined.
Anyway, y' = (x^28x20)/(x4)^2
y'=0 when x = 2,10
y' undefined when x = 4
how did you come up with 5/4 ?