Question 7217
5! is shorthand for 5x4x3x2x1, which is called a "factorial"


so, 9! is 9x8x7x6x5x4x3x2x1 etc


Backwards E means "there exists".


I cannot write "backwards E" so i shall write 3 instead:


3x means "there is/are x-values that..." and then you are given some function or qualifier.


Hope that helps.


jon.