Tìm x biết
a) 0,5x-2/3x=7/12
b) (X+3)^2=9/25
c) 7^x+2+2=345
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DC
3
11 tháng 4 2019
\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\Rightarrow x\cdot\left(\frac{3}{6}-\frac{4}{6}\right)=\frac{7}{12}\)
\(\Rightarrow x\cdot\left(-1\right)=\frac{7}{12}\Rightarrow x=\frac{7}{12}:\left(-1\right)=\frac{7}{-12}\)
\(c,\frac{\left(x-5\right)}{12}\cdot\frac{9}{29}=\frac{-6}{29}\Rightarrow\frac{\left(x-5\right)}{12}=\frac{-6}{29}:\frac{9}{26}\)
\(\frac{\Rightarrow\left(x-5\right)}{12}=\frac{-6}{9}=\frac{-2}{3}\Rightarrow x-5=-\frac{2}{3}\cdot12\)
\(\Rightarrow x-5=\frac{-24}{3}=-8\Rightarrow x=-8+5=-3\)
BA
11 tháng 4 2019
\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow-\frac{1}{6}x=\frac{7}{12}\)
\(\Rightarrow x=-\frac{7}{2}\)
\(c,\frac{x-5}{12}\cdot\frac{9}{29}=-\frac{6}{29}\)
\(\Rightarrow\frac{x-5}{12}=-\frac{2}{3}\)
\(\Rightarrow x-5=12.\left(-\frac{2}{3}\right)\)
\(\Rightarrow x-5=-8\)
\(\Rightarrow x=-3\)
DT
29 tháng 1 2019
a. x- (17 - x) = x-7
x-17+x = x+7
2x-17=x+7
2x-x= 7+17
x= 24
b. 9-25=(7-x)-(25+7)
-16=7-x-25-7
-16=-x-25
x= -25 + 16
x = -9
c. (-12)^2 .x = 56 + 10.13.x
144x = 56 + 130x
144x - 130x = 56
14x=56
x= 56 : 14
x= 4
d. 4/24 : (3x-2) = -3
4/24 = -3.(3x-2)
4/24 = -9x + 6
9x = 6 - 4/24
9x = 35/6
x= 35/6 :9
x= 35/54
e. 5/-45 chia hay nhân với (-3-2x) nhỉ
29 tháng 3 2015
dễ mà bn, ta sử dụng tính chất phân phối của phép trừ đối với phép nhân:
0,5=\(\frac{1}{2}\)
\(\frac{1}{2}\)x - \(\frac{2}{3}\)x = \(\frac{7}{12}\)
x ( \(\frac{1}{2}\)- \(\frac{2}{3}\)) = \(\frac{7}{12}\)
x . \(\frac{-1}{6}\)= \(\frac{7}{12}\)
x = \(\frac{7}{12}\): \(\frac{-1}{6}\)
x = \(\frac{7}{12}\). -6
x = \(-3\frac{1}{2}\)
( like cho mk lunk ha, bài này dễ, kiểm tra lại ha! Nếu mk làm sai thì còn sửa nữa!!!!!!!!!)
27 tháng 6 2022
a: =>1/2x-2/3x=7/12
=>-1/6x=7/12
hay x=-7/2
b: \(\Leftrightarrow x=-\dfrac{5}{2}\cdot\dfrac{13}{3}=\dfrac{-65}{6}\)
c: =>x=13/15:11/2=26/165
d: =>3/7x+1=1/7
=>3/7x=-6/7
hay x=-2
22 tháng 6 2016
\(a,\left(\frac{3}{8}+-\frac{3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
= \(\left(-\frac{3}{8}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
= \(\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)
= \(\frac{1}{4}+\frac{1}{2}\)
= \(\frac{3}{4}\)
b)\(-\frac{7}{3}.\frac{5}{9}+\frac{4}{9}.\left(-\frac{3}{7}\right)+\frac{17}{7}\)
=\(-\frac{35}{27}+\left(-\frac{4}{21}\right)+\frac{17}{7}\)
= \(-\frac{35}{27}+\frac{47}{21}\)
= \(\frac{178}{189}\)
c) \(\frac{117}{13}-\left(\frac{2}{5}+\frac{57}{13}\right)\)
= \(\frac{117}{13}-\frac{311}{65}\)
= \(\frac{274}{65}\)
d) \(\frac{2}{3}-0,25:\frac{3}{4}+\frac{5}{8}.4\)
= \(\frac{2}{3}-\frac{1}{4}:\frac{3}{4}+\frac{5}{8}.4\)
= \(\frac{2}{3}-\frac{1}{3}+\frac{5}{2}\)
= \(\frac{1}{3}+\frac{5}{2}\)
= \(\frac{17}{6}\)
4 tháng 4 2018
a, \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
=> \(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\)
=>\(\frac{-1}{6}x=\frac{7}{12}\)=> \(x=\frac{7}{12}:\frac{-1}{6}=\frac{-7}{2}\)
b, \(x:\frac{13}{3}=-2,5\)
=>\(x=\left(-2,5\right):\frac{13}{3}=\frac{-7,5}{13}\)
c, \(5,5x=\frac{13}{15}\)
=>\(x=\frac{13}{15}:5,5=\frac{13}{82,5}\)
d, \(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)
=>\(\left(\frac{3x}{7}+1\right)=\frac{-1}{28}:\left(-4\right)=\frac{1}{7}\)
=>\(\frac{3x}{7}=\frac{1}{7}-1=\frac{-6}{7}\)
=>\(3x=-6\)
=> \(x=\left(-6\right):3=-3\)
5 tháng 10 2020
Bài 1 :
a) \(\frac{12}{21}-\frac{3}{7}+\left(-\frac{2}{3}\right)=\frac{4}{7}-\frac{3}{7}+\left(-\frac{2}{3}\right)=\frac{1}{7}-\frac{2}{3}=-\frac{11}{21}\)
b) \(\left(-\frac{25}{13}\right)+\left(-\frac{9}{17}\right)+\frac{12}{13}+\left(-\frac{25}{17}\right)\)
\(=\left[\left(-\frac{25}{13}\right)+\frac{12}{13}\right]+\left[\left(-\frac{9}{17}\right)+\left(-\frac{25}{17}\right)\right]\)
\(=-1+\left(-2\right)=-1-2=-3\)
c) \(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}-\frac{5}{9}\cdot\frac{3}{13}=\frac{5}{9}\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)=\frac{5}{9}\cdot1=\frac{5}{9}\)
Bài 2 :
a) \(\frac{2}{3}x+\frac{5}{7}=\frac{3}{10}\)
=> \(\frac{2}{3}x=\frac{3}{10}-\frac{5}{7}=-\frac{29}{70}\)
=> \(x=\left(-\frac{29}{70}\right):\frac{2}{3}=\left(-\frac{29}{70}\right)\cdot\frac{3}{2}=-\frac{87}{140}\)
b) \(x:\frac{5}{2}-\frac{1}{2}=-\frac{2}{3}\)
=> \(x:\frac{5}{2}=-\frac{2}{3}+\frac{1}{2}=-\frac{1}{6}\)
=> \(x=\left(-\frac{1}{16}\right)\cdot\frac{5}{2}=-\frac{5}{32}\)
c) Bạn chỉ cần xét hai trường hợp âm và dương thôi :>
1 tháng 7 2023
a: =>3/2x=64/15
=>x=128/45
b: =>-1/6x=7/12
=>x=-7/2
c: =>11/2*x=1/2
=>x=1/2:11/2=1/11
a/ \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\)
\(x.\left(-\frac{1}{6}\right)=\frac{7}{12}\)
\(x=\frac{7}{12}:\left(-\frac{1}{6}\right)\)
\(x=\frac{7}{12}.\left(-6\right)=-\frac{7}{2}\)
b/ \(\left(x+3\right)^2=\frac{9}{25}\)
\(\left(x+3\right)^2=\left(\frac{3}{5}\right)^2\)
\(\Rightarrow x+3=\frac{3}{5}\)
\(x=\frac{3}{5}-3=\frac{3}{5}-\frac{15}{5}=-\frac{12}{5}\)