A function f having domain the closed interval [a, b] is defined to be convex on the closed interval [a, b] if and only if f(ta+ (1-t)b)≤tf(a) + (1-t)f(b) for any t between zero and one inclusive (i.e., 0≤t≤1). Use this definition to prove that the function f(x) =x2is convex on the closed interval [0,2].