\(\frac{x-2}{12}+\frac{x-2}{20}+\frac{x-2}{30}+..+\frac{x-2}{72}=\frac{16}{9}\)

\(\Rightarrow\left(x-2\right).\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{72}\right)=\frac{16}{9}\)

\(\Rightarrow\left(x-2\right).\left(\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{8.9}\right)=\frac{16}{9}\)

\(\Rightarrow\left(x-2\right).\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{8}-\frac{1}{9}\right)=\frac{16}{9}\)

\(\Rightarrow\left(x-2\right).\left(\frac{1}{3}-\frac{1}{9}\right)=\frac{16}{9}\)

\(\Rightarrow x-2=0\Rightarrow x=2\)

sai rồi nha hoàng trung kiên

Ta có : 

\(\frac{x-2}{12}+\frac{x-2}{20}+\frac{x-2}{30}+\frac{x-2}{42}+\frac{x-2}{56}+\frac{x-2}{72}=\frac{16}{9}\)

\(\Leftrightarrow\)\(\left(x-2\right)\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\right)=\frac{16}{9}\)

\(\Leftrightarrow\)\(\left(x-2\right)\left(\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}\right)=\frac{16}{9}\)

\(\Leftrightarrow\)\(\left(x-2\right)\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\right)=\frac{16}{9}\)

\(\Leftrightarrow\)\(\left(x-2\right)\left(\frac{1}{3}-\frac{1}{9}\right)=\frac{16}{9}\)

\(\Leftrightarrow\)\(\left(x-2\right).\frac{2}{9}=\frac{16}{9}\)

\(\Leftrightarrow\)\(x-2=\frac{16}{9}:\frac{2}{9}\)

\(\Leftrightarrow\)\(x-2=\frac{16}{9}.\frac{9}{2}\)

\(\Leftrightarrow\)\(x-2=\frac{8}{1}.\frac{1}{1}\)

\(\Leftrightarrow\)\(x-2=8\)

\(\Leftrightarrow\)\(x=8+2\)

\(\Leftrightarrow\)\(x=10\)

Vậy \(x=10\)

Chúc bạn học tốt ~ 

tìm x biết:

1/3+2/5.(x-1) = 4

=> 2/5.(x-1) = 4 - 1/3 = 11/3

=> x-1 = 11/3 : 2/5 = 55/6

=> x= 55/6 + 1 = 61/6

1/2-1/3:3x0 = -5 

?????? đề hay thật

a) \(\frac{45-\left(3x+9\right)}{13}=42\)

\(\Leftrightarrow45-\left(3x+9\right)=546\)

\(\Leftrightarrow3x+9=-501\)

\(\Leftrightarrow3x=-510\)

\(\Leftrightarrow x=-170\)

b) \(\left(x+1\right)+\left(2x+2\right)+...+\left(20x+20\right)=1050\)

\(\Leftrightarrow x+1+2x+2+...+20x+20=1050\)

\(\Leftrightarrow\left(x+1\right)+2\left(x+1\right)+....+20\left(x+1\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left(1+2+3+...+20\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left[\frac{\left(20+1\right).20}{2}\right]=1050\)

\(\Leftrightarrow\left(x+1\right).210=1050\)

\(\Leftrightarrow x+1=5\)

\(\Leftrightarrow x=4\)

BT1 :thực hành phép tính

4/3+-11/31+3/10-20/31-2/5 = 7/30

7/12-1/-16+3/4 = 67/48

2/11.-5/4+-9/11.5/4+ 1 và 3/4 = -1/4 * và 3/4 là sao bạn *

-9/27-25/75 = -2/3

a: -x+5/9=-1/3

nên x=5/9+1/3=5/9+3/9=8/9

b: \(\Leftrightarrow\dfrac{1}{5}+\dfrac{1}{10}+\dfrac{11}{15}< x< \dfrac{1}{2}+\dfrac{13}{12}+\dfrac{1}{3}\)

=>31/30<x<23/12

mà x là số nguyên

nên \(x\in\varnothing\)

c: x+5/3=1/81

nên x=1/81-135/81=-134/81

\(\left(\frac{3}{20}+\frac{1}{20}-x\right):\frac{32}{9}=\frac{21}{128}\)

\(\Leftrightarrow\frac{4}{20}-x=\frac{21}{128}.\frac{32}{9}\)

\(\Leftrightarrow\frac{1}{5}-x=\frac{7}{12}\)

\(\Leftrightarrow x=\frac{1}{5}-\frac{7}{12}\)

\(\Leftrightarrow x=-\frac{23}{60}\)

Vậy \(x=\frac{-23}{60}\)

Bài làm

\(\left(\frac{3}{20}+\frac{1}{20}-x\right):\frac{32}{9}=\frac{21}{128}\)

\(\left(\frac{3}{20}+\frac{1}{20}-x\right)=\frac{21}{128}.\frac{32}{9}\)

\(\frac{4}{20}-x=\frac{7}{4}.\frac{1}{3}\)

\(\frac{4}{20}-x=\frac{7}{12}\)

\(x=\frac{4}{20}-\frac{7}{12}\)

\(x=\frac{12}{60}-\frac{35}{60}\)

\(x=-\frac{23}{60}\)

Vậy \(x=-\frac{23}{60}\)

\(x=-\frac{37}{15}\)