Question

tìm x:

\(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{x.\left(x+2\right)}=\frac{4}{9}\)   

giúp mik với!!!!!!!!!!!!!!!!!!!!

Answer 1

bạn tk mình một lần cho mình biết đi mình chưa được ai tk lần nào

Answer 2

Nhưng bn phải trả lời chứ

Answer 3

\(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+....+\frac{1}{x}-\frac{1}{x+2}=\frac{4}{9}\)

\(\frac{1}{2}-\frac{1}{x+2}=\frac{4}{9}\)

\(\frac{1}{x+2}=\frac{1}{2}-\frac{4}{9}\)

\(\frac{1}{x+2}=\frac{1}{18}\)

=>x+2=18

x=18-2

x=16

Answer 4

nhưng mới có lớp 3 à huhu

Answer 5

\(\frac{2}{2.4}+\frac{2}{4.6}+....+\frac{2}{x.\left(x+2\right)}=\frac{4}{9}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+......+\frac{1}{x}-\frac{1}{x+2}=\frac{4}{9}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+2}=\frac{4}{9}\)

\(\Rightarrow\frac{1}{x+2}=\frac{1}{2}-\frac{4}{9}\)

\(\Rightarrow\frac{1}{x+2}=\frac{1}{9}\)

\(\Rightarrow x+2=9\Rightarrow x=9-2\Rightarrow x=7\)

Vậy \(x=7\)

Answer 6

\(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{x\left(x+2\right)}=\frac{4}{9}\)

\(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{x}-\frac{1}{x+2}=\frac{4}{9}\)

\(\frac{1}{2}-\frac{1}{x+2}=\frac{4}{9}\)

\(\frac{1}{x+2}=\frac{1}{2}-\frac{4}{9}\)

\(\frac{1}{x+2}=\frac{1}{18}\)

=>x + 2 = 18

x = 18 - 2

x = 16