Question 896054
Although I did a couple or maybe three of these within last few minutes, the ambiguity in your expression may be a problem.  WHAT is the actual expression you have?


{{{4-sqrt(5x)/2}}}?


{{{4-sqrt(5x/2)}}} ?


My guess, it's the second one.
My other solutions for your questions should be more than enough to understand what to do here.