Problem 2 (1 marks). Prove the following proposition. Proposition 1 Let U C R" be open. If f: U R is differentiable at x E U, there are positive real numbers and K such that ||u x|| < n implies If (u) f(x)| < K ||u x||. Hint: Try using the e, & definition with e = 1. And recall that for any two real numbers a, b, one has lal-1 < la-b.