Help I don’t understand functions at all

Translate the word phrase into a math expression. 15 fewer than the product of 4 and a number. (pls immediately)

Explain why the function is discontinuous at the given number a. (select all that apply.) f(x) = 1 x + 1 a = −1 f(−1) is undefined. lim x→−1+ f(x) and lim x→−1− f(x) exist, but are not equal. lim x→−1 f(x) does not exist. f(−1) and lim x→−1 f(x) exist, but are not equal. none of the above

Which best explains why this triangle is or is not a right triangle?