Question

Tính: 5/2.4 + 5/4.6 +5/6.8+....+5/98.100

Giúp tớ làm bài này nhé! Nhớ làm cách giải luôn!

 

Answer 1

\(A=\frac{5}{2.4}+\frac{5}{4.6}+...+\frac{5}{98.100}\)

\(A=\frac{5}{2}.\left(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{98.100}\right)\)

\(A=\frac{5}{2}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{98}-\frac{1}{100}\right)\)

\(A=\frac{5}{2}.\left(1-\frac{1}{100}\right)\)

\(A=\frac{5}{2}.\frac{99}{100}=\frac{99}{40}\)

Answer 2

1/1×2+1/2×3+1/3×4+...+1/45×46+1/46+47