Question

\(C=\frac{3}{1\times4}+\frac{3}{4\times7}+\frac{3}{7\times10}+......+\frac{3}{31\times34}=?????\)

trình bày rõ ràng ai nhanh và đung mik tick tận tay ^_-

Answer 1

\(C=\frac{3}{1\times4}+\frac{3}{4\times7}+\frac{3}{7\times10}+...+\frac{3}{31\times34}\)

\(=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{31}-\frac{1}{34}\)

\(=1-\frac{1}{34}=\frac{33}{34}\)

Answer 2

99/34

Answer 3

\(C=3-\frac{3}{4}+\frac{3}{4}-\frac{3}{7}+\frac{3}{7}-\frac{3}{10}+...+\frac{3}{31}-\frac{3}{34}\)

\(C=3+\frac{3}{34}=\frac{99}{34}\)