Question

Answer 1

bn cần giúp bài nào

Answer 2

Giải  giup mình bài  cuoi với 

Answer 3

bài cuối là bài nào ??

Answer 4

( 1/1 nhân 2 + 1 /2  nhan3 + 1/3 nhân  4.........

Answer 5

Bài 4:

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

\(\Leftrightarrow\left(1-\dfrac{1}{10}\right)\cdot100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Leftrightarrow90-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\Leftrightarrow\dfrac{5}{2}:\left(x+\dfrac{206}{102}\right):\dfrac{1}{2}=1\)

\(\Leftrightarrow\dfrac{5}{2}:\left(x+\dfrac{206}{102}\right)=2\)

\(\Leftrightarrow\left(x+\dfrac{206}{102}\right)=\dfrac{5}{4}\)

\(\Leftrightarrow x=\dfrac{-157}{204}\)

Answer 6

\(\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{9.10}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]:\dfrac{1}{2}=89\)

\(\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{9.10}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=89.\dfrac{1}{2}\)

\(\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{9.10}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=44,5\)

\(\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{9}-\dfrac{1}{10}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=44,5\)

\(\left(1-\dfrac{1}{10}\right).100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=44,5\)

\(\dfrac{9}{10}.100-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=44,5\)

\(90-\left[\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)\right]=44,5\)

\(\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)=90-44,5\)

\(\dfrac{5}{2}:\left(x+\dfrac{206}{100}\right)=45,5\)

\(x+\dfrac{206}{100}=\dfrac{5}{2}:45,5\)

\(x+\dfrac{206}{100}=\dfrac{5}{91}\)

\(x=\dfrac{5}{91}-\dfrac{206}{100}=\dfrac{-9123}{4550}\)