Question

Tìm X trong biểu thức sau

( 1/1,2 + 1/2,3 + 1/3,4 + ... + 1/8,9 + 1/9,10 ) * 100 - [ 5/2 : ( x + 206/100) ] : 1/2 = 89

 

Answer 1

coi lại đề bài đi bạn

Answer 2

Ta có: \(\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{8\cdot9}+\dfrac{1}{9\cdot10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Leftrightarrow100\cdot\left(1-\dfrac{1}{10}\right)-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Leftrightarrow\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=1\)

\(\Leftrightarrow\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)=2\)

\(\Leftrightarrow x+\dfrac{103}{50}=\dfrac{5}{4}\)

hay \(x=\dfrac{331}{100}\)