Number patterns for 70 65 55 50?

Answer 1

There are infinitely many polynomials of order 4 that will give these as the first four numbers and any one of these could be "the" rule. Short of reading the mind of the person who posed the question, there is no way of determining which of the infinitely many solutions is the "correct" one.
One possible solution, based on a polynomial of order 3 isU(n) = 6/5*(2*n^3 - 15*n^2 + 25*n + 72) for n = 1, 2, 3, ...

Answer 2

Each integer is five less than the one preceding it.