Mathswatch question please help

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Farnesene is a sesquiterpene. how many different isomers arising from double-bond isomerizations are possible? g

What are the possible rational zeros of [tex]f(x) = x^4+2x^3-3x^2-4x+18[/tex]