Find all constants a such that the vectors (a, 2) and (a, -2) are orthogonal
please help​

Fiona and her friends are playing a game by guessing where a coin will land when it is randomly dropped inside the square shown below. fiona guesses that the coin is likely to land in the blue area. which explains whether or not fiona is correct and why?

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?

I'm confused on this could anyone me and show me what i need to do to solve it.