Chứng minh 1/2^2 + 1/3^2 +...+ 1/99^2 <  3/4

Many years ago, there was a very beautiful princess who lived in a castle. The princess had a problem with her legs and couldn't walk. One day, a prince visited the castle and met the beautiful princess. He gave her an apple and said, "This magic apple can make you walk!" The princess was very happy. She ate the apple. Then the next morning, she got up and was so surprised because she could walk and run and dance.  In the end, the prince and the princess got married and lived happily ever after.