Question

[RHYDER]

M = 4/(1.3)^2 + 8/(3.5)^2 + ... + 24/(11.13)^2

giúp với

Answer 1

[Nguyễn Lê Phước Thịnh]

\(M=\frac{4}{\left(1\cdot3\right)^2}+\frac{8}{\left(3\cdot5\right)^2}+\cdots+\frac{24}{\left(11\cdot13\right)^2}\)

\(=\frac12\left(\frac{8}{1^2\cdot3^2}+\frac{16}{3^2\cdot5^2}+\cdots+\frac{48}{11^2\cdot13^2}\right)\)

\(=\frac12\left(\frac{8}{1\cdot9}+\frac{16}{9\cdot25}+\cdots+\frac{48}{121\cdot169}\right)\)

\(=\frac12\left(1-\frac19+\frac19-\frac{1}{25}+\cdots+\frac{1}{144}-\frac{1}{169}\right)\)

\(=\frac12\left(1-\frac{1}{169}\right)=\frac12\cdot\frac{168}{169}=\frac{84}{169}\)

Answer 2

[RHYDER]

chịu

Answer 3

[Bế Phạm Bảo Ngọc]

tên anh trai say hi đó

rhyder