Đáp án:
$\frac{1}{3^{2} }$+$\frac{1}{4^{2} }$+$\frac{1}{5^{2} }$+...+$\frac{1}{160^{2} }$<$\frac{1}{2}$
⇔$\frac{1}{3^{2} }$+$\frac{1}{4^{2} }$+$\frac{1}{5^{2} }$+...+$\frac{1}{160^{2} }$<$\frac{158}{316}$
⇔$\frac{1}{3^{2} }$+$\frac{1}{4^{2} }$+$\frac{1}{5^{2} }$+...+$\frac{1}{160^{2} }$<$\frac{1}{316}$ .158
Vì $\frac{1}{3^{2} }$<$\frac{1}{316}$;$\frac{1}{4^{2} }$<$\frac{1}{316}$;...
⇒$\frac{1}{3^{2} }$+$\frac{1}{4^{2} }$+$\frac{1}{5^{2} }$+...+$\frac{1}{160^{2} }$<$\frac{1}{316}$ .158
⇒$\frac{1}{3^{2} }$+$\frac{1}{4^{2} }$+$\frac{1}{5^{2} }$+...+$\frac{1}{160^{2} }$<$\frac{1}{2}$
Xin hay nhất.
