Question

Cho A= \(\dfrac{4}{2.4}\)+\(\dfrac{4}{4.6}\)+\(\dfrac{4}{6.8}\)+...+\(\dfrac{4}{46.48}\)+\(\dfrac{4}{48.50}\)

Answer 1

\(A=2\left(\dfrac{2}{2.4}+\dfrac{2}{4.6}+...+\dfrac{2}{48.50}\right)\)

\(=2\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)\)

\(=2\left(\dfrac{1}{2}-\dfrac{1}{50}\right)\)

\(=2\times\dfrac{12}{25}=\dfrac{24}{25}\)

Answer 2

\(=>A=4.\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{8}+...+\dfrac{1}{46}-\dfrac{1}{48}+\dfrac{1}{48}-\dfrac{1}{50}\right)\)

\(A=4.\left(\dfrac{1}{2}-\dfrac{1}{50}\right)=4.\left(\dfrac{25}{50}-\dfrac{1}{50}\right)=\dfrac{4.24}{50}=\dfrac{48}{25}\)

Answer 3

\(A=\frac{2}{2\times4}+\frac{2}{4\times6}+\frac{2}{6\times8}+\) \(...\) \(+\frac{2}{46\times48}+\frac{2}{48\times50}\)

Answer 4

A= 4/2.4 + 4/4.6 + 4/6.8 +…+ 4/46.48 + 4/48.50

A= 4. ( 1/2.4 + 1/4.6 + 1/6.8 +…+ 1/46.48 + 1/48.50)

2.A= 4. ( 2/2.4 + 2/4.6 + 2/6.8 +…+ 2/46.48 + 2/48.50)

2.A = 4. (1/2 -1/4 + 1/4 -1/6 + 1/6 - 1/8 +…+1/46 -1/48 +1/48 - 1/50)

2.A= 4. (1/2 - 1/50)

2.A= 4. 12/25

A= 12/25 : 2

A= 6/25

Answer 5

A= 4/2.4 + 4/4.6 + 4/6.8 +…+ 4/46.48 + 4/48.50 

A= 4. ( 1/2.4 + 1/4.6 + 1/6.8 +…+ 1/46.48 + 1/48.50)

2.A= 4. ( 2/2.4 + 2/4.6 + 2/6.8 +…+ 2/46.48 + 2/48.50)

2.A = 4. (1/2 -1/4 + 1/4 -1/6 + 1/6 - 1/8 +…+1/46 -1/48 +1/48 - 1/50)

2.A= 4. (1/2 - 1/50) 

2.A= 4. 12/25

A= 48/25 : 2

A= 24/25

Answer 6

cho xin lỗi do kết quả trước đó chưa chia phân số