# Chebyshev approximation and linear programming

I'm trying to do the problem below and I cannot understand what (ii), (iv) and (v) are asking for.

From my understanding, Chebyshev approximation is used to transform a norm approximation problem in $$l_{\infty}$$ to a linear programming problem. So how should I apply Chebyshev approximation to $$l_{1}$$ and $$l_{2}$$ norm? Moreover, how should I "reformulate" the Chebyshev approximation problem using $$l_{1}$$ and $$l_{\infty}$$ as a LP?