How do I determine whether each trinomial is a difference of two squares -and it would be helpful if you can tell me if 4x−9y is a difference of two squares or not
-and it would be helpful if you can tell me if 25m^2+16 is a difference of two squares or not

The patient recovery time from a particular surgical procedure is normally distributed with a mean of 5.2 days and a standard deviation of 1.7 days. what is the probability of spending more than 2 days in recovery? (round your answer to four decimal places.)