Someone help me out on these pages

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?

True or false: the graph of y=f(bx) is a horizontal compression of the graph y=f(x) if b< 1

Joe has some money in his bank account he deposits 45$ write an expression that represents the amount of money in joe's account