250. (1/5 - 1/6)^2 ? 250 . (1/5)^2 -1/6

Lời giải:

Ta có: \(250\,.\,{\left( {\frac{1}{5} - \frac{1}{6}} \right)^2} = 250\,.\,{\left( {\frac{1}{{30}}} \right)^2} = 250\,.\,\frac{1}{{900}} = \frac{5}{{18}}\);

\(250\,.\,{\left( {\frac{1}{5}} \right)^2} - \frac{1}{6} = 250\,.\,\frac{1}{{25}} - \frac{1}{6} = 10 - \frac{1}{6} = \frac{{59}}{6} = \frac{{177}}{{18}}\).

Vì 5 < 177 nên \(\frac{5}{{18}} < \frac{{177}}{{18}}\) hay \(250\,.\,{\left( {\frac{1}{5} - \frac{1}{6}} \right)^2} < 250\,.\,{\left( {\frac{1}{5}} \right)^2} - \frac{1}{6}\)

250.(15-16)2 <   250.(15)2-16;