Question

[Phan Anh Kiệt]

Tìm x

2x-3=x+\(\frac{1}{2}\)

4x-(2x+1)=3-\(\frac{1}{3}\) +x

Tính

a \(\frac{1}{1\cdot4}\) +\(\frac{1}{4\cdot7}\) +\(\frac{1}{7\cdot10}\) +....+\(\frac{1}{100\cdot103}\)

b \(\frac{8}{9}\) -\(\frac{1}{72}\) -\(\frac{1}{56}\) -\(\frac{1}{42}\) -....-\(\frac{1}{6}\) -\(\frac{1}{2}\)

Answer 1

[Ngô Bá Hùng]

a)\(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{100.103}\\ =\frac{1}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{100}-\frac{1}{103}\right)\\ =\frac{1}{3}.\left(1-\frac{1}{103}\right)\\ =\frac{1}{3}.\frac{102}{103}\\ =\frac{34}{103}\)

Answer 2

[bé Bắp]

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