Now, f0(x) and g0(x) are both positive for x < µg, and they are both negative for x > µf . Hence h(x) = pf(x) + qg(x) has the properties that (a) h0(x) > 0 for x < µg; (b) h0(x) < 0 for x > µf , and (c) h00(x) < 0 for x ∈ [µg, µf]. From (a) and (b) it follows that h must achieve its maximum in the interval [µg, µf], and from (c) it follows that there is a unique local maximum in this
interval. Hence setting ε0 = δ proves (i).