Chứng minh

Bài 1: CMR :A=$\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{199}+\frac{1}{200}>\frac{7}{12}$
Bài 2: CMR: $\frac{1}{6}<\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{{100}^2}<\frac{1}{4}$