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27 tháng 6 2017
a) \(\left(x-1\right):3=2^3\) \(\Leftrightarrow\) \(\left(x-1\right):3=8\) \(x+1=24\) \(\Leftrightarrow\) \(x=23\) vậy \(x=23\)
b) \(12-2\left(x+5\right)=-10\) \(\Leftrightarrow\) \(12-2x-10=-10\)
\(\Leftrightarrow\) \(-2x=-12\) \(\Leftrightarrow\) \(x=6\) vậy \(x=6\)
c) \(x-12\left(x+5\right)=-10\) \(\Leftrightarrow\) \(x-12x-60=-10\)
\(\Leftrightarrow\) \(-11x=50\) \(\Leftrightarrow\) \(x=\dfrac{50}{-11}\) vậy \(x=\dfrac{50}{-11}\)
e) \(13-x:2=10\Leftrightarrow-x:2=-3\Leftrightarrow x=\dfrac{3}{2}\)
f) \(\left|12-x\right|-7=5\)
th1 : \(x\le12\) thì \(\left|12-x\right|-7=5\) \(\Leftrightarrow\) \(12-x-7=5\) \(\Leftrightarrow\) \(-x=0\Leftrightarrow x=0\)
th2 : \(x>12\) thì \(\left|12-x\right|-7=5\) \(\Leftrightarrow\) \(x-12-7=5\) \(\Leftrightarrow\) \(x=24\) vậy \(x=0;x=24\)
i) \(x^2-7=2\Leftrightarrow x^2=9\Leftrightarrow x=3\) vậy \(x=3\)
k) \(x^3-4=-12\) \(\Leftrightarrow\) \(x^3=-8\) \(\Leftrightarrow x=-2\) vậy \(x=-2\)
27 tháng 6 2017
a)\(\left(x-1\right):3=2^3\Rightarrow x-1=2^3.3=24\Rightarrow x=25\)
b)\(12-2\left(x+5\right)=-10\Leftrightarrow12-2x-10=-10\Rightarrow2-2x=-10\Rightarrow2x=12\Rightarrow x=6\)c)\(x-12\left(x+5\right)=-10\Rightarrow x-12x-60=-10\Rightarrow-11x-60=-10\Rightarrow-11x=-70\Rightarrow x=\dfrac{70}{-11}\)d)\(6-\left|x\right|=5\Rightarrow\left|x\right|=1\Rightarrow x=\left\{\pm1\right\}\)
Làm nốt nha
28 tháng 6 2017
a) x-12:(-2)=4
=> x-12=-8
=> x=4
b ) 6-|x| = 5
=> /x/=1
=> x=1;-1
c ) 7⋮ ( x-3)
=> (x-3) thuộc Ư(7)
=> x-3=1 => x=4
=> x-3=-1 => x=2
=> x-3=7 => x= 10
=> x-3=-7 => x=-4
d ) 3⋮ ( 2x+1 )
=> (2x+1) thuộc Ư(3)
=> (2X+1)= 1 => x= 0
=> (2x+1)=-1 => x= -1
=> 2x+1= 3 => x= 1
=> 2x+1=-3 => x= -2
28 tháng 6 2017
a) \(x-12:\left(-2\right)=4\Rightarrow x-\left(-6\right)=4\Rightarrow x=\left(-6\right)+4=-2\)
b) \(6-\left|x\right|=5\Rightarrow\left|x\right|=6-5=1\Rightarrow x=\left\{\pm1\right\}\)
c)\(7⋮x-3\Rightarrow x-3\inƯ\left(7\right)\)
\(Ư\left(7\right)=\left\{\pm1;\pm7\right\}\)
\(x=\left\{4;2;10;-4\right\}\)
d) \(3⋮2x+1\Rightarrow2x+1\inƯ\left(3\right)\)
\(Ư\left(3\right)=\left\{\pm1;\pm3\right\}\)
\(x\in\left\{0;-1;1;-2\right\}\)
9 tháng 8 2019
\(bai1:a,\frac{3}{7}\cdot\frac{-5}{9}+\frac{4}{9}\cdot\frac{3}{7}-\frac{3}{7}\cdot\frac{8}{9}\)
\(< =>\frac{-15}{63}+\frac{12}{63}-\frac{24}{63}\)
\(< =>\frac{-15+12-24}{63}\)
\(< =>\frac{-3}{7}\)
\(b,1\frac{13}{15}\cdot0,75-\left(\frac{11}{20}+25\%\right):\frac{7}{5}\)
\(< =>\frac{28}{15}\cdot\frac{3}{4}-\left(\frac{11}{20}+\frac{1}{4}\right):\frac{7}{5}\)
\(< =>\frac{7}{5}-\frac{4}{5}:\frac{7}{5}\)
\(< =>\frac{7}{5}-\frac{4}{7}\)
\(< =>\frac{29}{35}\)
\(bai2:\)
\(a,\frac{-3}{4}\cdot x-\frac{4}{10}=\frac{1}{5}\)
\(< =>\frac{-3}{4}\cdot x=\frac{1}{5}+\frac{4}{10}\)
\(< =>\frac{-3}{4}\cdot x=\frac{3}{5}\)
\(< =>x=\frac{3}{5}:\frac{-3}{4}\)
\(< =>x=\frac{-4}{5}\)
\(b,3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{19}:\frac{12}{19}\)
\(< =>3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{12}\)
\(< =>\left[3\left(x-\frac{1}{3}\right)\right]=\frac{1}{12}< =>x-\frac{1}{3}=\frac{1}{12}:3=\frac{1}{36}=>x=\frac{1}{36}+\frac{1}{3}=>x=\frac{13}{36}\)
\(< =>\left[\frac{1}{3}\cdot x\right]=\frac{1}{12}< =>x=\frac{1}{12}:\frac{1}{3}=>x=\frac{1}{4}\)
MM
9 tháng 8 2019
Bài 1:
a)\(\frac{3}{7}.\frac{-5}{9}+\frac{4}{9}.\frac{3}{7}-\frac{3}{7}.\frac{8}{9}\) b,\(1\frac{13}{15}.0,75-\left(\frac{11}{20}+25\%\right):\frac{7}{5}\)
\(=\frac{3}{7}.(\frac{-5}{9}+\frac{4}{9}-\frac{8}{9})\) \(=\frac{28}{15}.\frac{3}{4}-\left(\frac{11}{20}+\frac{5}{20}\right):\frac{7}{5}\)
\(=\frac{3}{7}.\frac{-9}{9}\) \(=\frac{7}{5}-\frac{4}{5}:\frac{7}{5}\)
\(=\frac{-3}{7}\) \(=\frac{7}{5}-\frac{4}{7}\)
\(=\frac{29}{35}\)
Bài 2:
a)\(\frac{-3}{4}x-\frac{4}{10}=\frac{1}{5}\) b,\(3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{19}:\frac{12}{19}\)
\(\frac{-3}{4}x\) \(=\frac{1}{5}+\frac{4}{10}\) \(3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{12}\)
\(\frac{-3}{4}x\) \(=\frac{3}{5}\) \(\left(x.3-\frac{1}{3}.3\right)+\frac{1}{3}x=\frac{1}{12}\)
\(x\) \(=\frac{3}{5}:\frac{-3}{4}\) \(\left(x.3-1\right)+\frac{1}{3}x=\frac{1}{12}\)
\(x\) \(=\frac{4}{-5}\) \(x.\left(3+\frac{1}{3}\right)-1=\frac{1}{12}\)
\(x.\left(3+\frac{1}{3}\right)=\frac{1}{12}+1\)
\(x.\frac{10}{3}=\frac{13}{12}\)
\(x=\frac{13}{12}:\frac{10}{3}\)
\(x=\frac{13}{40}\)
GV
1
10 tháng 12 2016
a ) x +5 = -10
x = -10 -5
x = - 15
b) x - ( - 10 ) = 5
x = 5+(-10)
x = -5
c) \(\left|x\right|\) -5 = 3
\(\left|x\right|=8\)
x ϵ { -8 ; 8 }
d) 15 - ( - x ) = 20
Không có số tự nhiên x nào mà 15 ( - x ) = 20
e ) \(\left|x-4\right|=3-\left(-7\right)\\ \left|x-4\right|=10\\ \left|x\right|=14\\ x\in\left\{\pm14\right\}\)
f ) \(\left|x+5\right|=10-\left(-20\right)\\ \left|x+5\right|=30\\ \left|x\right|=25\\ x\in\left\{\pm25\right\}\)
21 tháng 10 2016
\(-12\left(x-5\right)+7\left(3-x\right)=5\)
\(-12x+60+21-7x=5\)
\(-19x+81=5\)
\(-19x=81-5=76\)
\(x=\frac{76}{-19}=-4\)
\(\Rightarrow x=-4\)
DT
5
28 tháng 1 2016
Ta có\(\frac{-15}{12}x+\frac{3}{7}=\frac{6}{5}x-\frac{1}{2}\)
=>\(\frac{-15}{12}x-\frac{6}{5}x=\frac{1}{2}-\frac{3}{7}\)
=>\(\left(\frac{-15}{12}-\frac{6}{5}\right)x=\frac{1}{14}\)
=>\(\frac{-49}{20}x=\frac{1}{14}\)
=>\(x=\frac{1}{14}:\frac{-49}{20}\)
=>\(x=\frac{-10}{343}\)
ND
5
31 tháng 5 2017
\(x=-\frac{5}{6}-\frac{7}{12}-\frac{-1}{3}\)
\(x=\frac{-13}{12}\)
Giải phương trình:
\(- 12 \left(\right. x - 5 \left.\right) + 7 \left(\right. 3 - x \left.\right) = 5\)Bước 1: Phân phối
\(- 12 x + 60 + 21 - 7 x = 5\)Bước 2: Gom các hạng tử giống nhau
\(- 12 x - 7 x + 60 + 21 = 5\) \(- 19 x + 81 = 5\)Bước 3: Trừ 81 hai vế
\(- 19 x = 5 - 81\) \(- 19 x = - 76\)Bước 4: Chia hai vế cho -19
\(x = \frac{- 76}{- 19}\) \(x = 4\)Đáp án cuối cùng:
\(\mathbf{x} = 4\)-12(x-5)+7(3-x)=5
=>-12x+60+21-7x=5
=>-19x+81=5
=>-19x=-76
=>x=4