I need help in this plis

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?

Which table represents a linear function? i'll give brainliest to first answer ^'^

Solve each equation using the quadratic formula. find the exact solutions. 6n^2 + 4n - 11