Question

[ĐẶNG THỊ VIỆT HÀ]

Bài 1: Tính hợp lý ( nếu có thể)                                                                        Bài 2:Tìm x biết

a, \(\left(4\frac{2}{3}-1\frac{1}{6}\right):\left(1,75+1\frac{1}{2}\right)\)                                                        a,\(\frac{4}{9}+x=\frac{-5}{3}\)

b, \(125\%-7\frac{1}{2}+0,5:\frac{4}{3}\)                                                                   b, \(2,4:\left(\frac{1}{2}.x-\frac{3}{4}\right)=\frac{3}{10}\)

c, \(\frac{11}{53}+\left(\frac{32}{47}+\frac{-10}{53}\right)+\frac{-64}{94}+\frac{1}{-53}+\frac{1}{3}\)                     c, \(\frac{x+1}{-8}=\frac{-2}{x+1}\)

d,  \(1\frac{1}{20}.\left(\frac{-2}{3}\right)^2+\left(0,8-\frac{8}{15}\right):\frac{-4}{17}\)                     d,\(\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{97.99}\right)-x=\frac{-100}{99}\)

Bài 3: Tìm x biết

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x\left(x+1\right)}=\frac{99}{100}\)

Giúp mik với đang cần gấp nha!!!^^

Answer 1

[xKraken]

Bài 3:

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x\left(x+1\right)}=\frac{99}{100}\)

\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{99}{100}\)

\(1-\frac{1}{x+1}=\frac{99}{100}\)

\(\frac{1}{x+1}=1-\frac{99}{100}\)

\(\frac{1}{x+1}=\frac{1}{100}\Leftrightarrow x+1=100\Rightarrow x=100-1=99\)

Chúc bạn học tốt !!!

Answer 2

[Edogawa Conan]

3. 

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x\left(x+1\right)}=\frac{99}{100}\)

=> \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{99}{100}\)

=> \(1-\frac{1}{x+1}=\frac{99}{100}\)

=> \(\frac{1}{x+1}=1-\frac{99}{100}\)

=> \(\frac{1}{x+1}=\frac{1}{100}\)

=> \(x+1=100\)

=> \(x=100-1\)

=> \(x=99\)

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