Question

Tinh tổng:

a) 2/1.3+2/3.5+2/5.7+.........2/99.101

b) 5/1.3+5/3.5+5/5.7+....................5/99.101

Answer 1

a)\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}=\left(1-\frac{1}{3}\right)+\left(\frac{1}{3}-\frac{1}{5}\right)+\left(\frac{1}{5}-\frac{1}{7}\right)+...+\left(\frac{1}{99}-\frac{1}{101}\right)\)

                                                               \(=1-\frac{1}{101}=\frac{100}{101}\)

b) \(\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{99.101}=\frac{2}{1.3}.\frac{5}{2}+\frac{2}{3.5}.\frac{5}{2}+\frac{2}{5.7}.\frac{5}{2}+...+\frac{2}{99.101}.\frac{5}{2}\)

                                                                \(=\frac{5}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\right)\)

                                                                \(=\frac{5}{2}.\frac{100}{101}=\frac{250}{101}\)

Answer 2

a)100/101

b)250/101

Answer 3

A)100/101

B)250/101

Answer 4

a) 2/1.3+2/3.5+2/5.7+.........2/99.101=100/101

b) 5/1.3+5/3.5+5/5.7+....................5/99.101=250/101

Answer 5

toán lớp 5 mà dễ vcl

Answer 6

làm hộ bài này voi

tính tổng C= 5+5^2+5^3+...+5^2017

Answer 7

2/1.3+2/3.5+2/5.7+........+2/99.101

1/1-1/3+1/3-1/5+1/5-1/7+......+1/99-1/101

1-1/101

100/101

Answer 8

ối dồi ôi

Answer 9

a)100/101 b)250/101