Question Number 107283 by mathmax by abdo last updated on 09/Aug/20
![f integrable continue on [a,b] let m =inf f(x) and M=sup f(x) (x ∈[a,b] prove that (b−a)^2 ≤∫_a ^b f(x)dx×∫_a ^b (dx/(f(x)))≤(((b−a)^2 )/4)(((m+M)^2 )/(mM))](https://www.tinkutara.com/question/Q107283.png)
$$\mathrm{f}\:\mathrm{integrable}\:\mathrm{continue}\:\mathrm{on}\:\left[\mathrm{a},\mathrm{b}\right]\:\mathrm{let}\:\mathrm{m}\:=\mathrm{inf}\:\mathrm{f}\left(\mathrm{x}\right)\:\mathrm{and}\:\mathrm{M}=\mathrm{sup}\:\mathrm{f}\left(\mathrm{x}\right) \\ $$$$\left(\mathrm{x}\:\in\left[\mathrm{a},\mathrm{b}\right]\:\mathrm{prove}\:\mathrm{that}\:\:\:\:\:\:\:\left(\mathrm{b}−\mathrm{a}\right)^{\mathrm{2}} \leqslant\int_{\mathrm{a}} ^{\mathrm{b}} \mathrm{f}\left(\mathrm{x}\right)\mathrm{dx}×\int_{\mathrm{a}} ^{\mathrm{b}} \:\frac{\mathrm{dx}}{\mathrm{f}\left(\mathrm{x}\right)}\leqslant\frac{\left(\mathrm{b}−\mathrm{a}\right)^{\mathrm{2}} }{\mathrm{4}}\frac{\left(\mathrm{m}+\mathrm{M}\right)^{\mathrm{2}} }{\mathrm{mM}}\right. \\ $$