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PN
24 tháng 8 2017
a) \(\left|x\right|< 1\Rightarrow-1< x< 1\Rightarrow x=0\)
b) \(\left|x+3\right|=0\)
\(\Leftrightarrow x+3=0\)
\(\Leftrightarrow x=-3\)
c) \(\left|x+2\right|=\left|12-10\right|\)
\(\Leftrightarrow\left|x+2\right|=2\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2=-2\\x+2=2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\left(-2\right)-2\\x=2-2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=0\end{matrix}\right.\)
d) \(\left|x+3\right|=2x-2\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x-2\ge0\\\left[{}\begin{matrix}x+3=2x-2\\x+3=\left(-2x\right)+2\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x\ge2\\\left[{}\begin{matrix}x-2x=-2-3\\x-\left(-2x\right)=2-3\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ge1\\\left[{}\begin{matrix}-x=-5\\3x=-1\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ge1\\\left[{}\begin{matrix}x=5\left(tm\right)\\x=\dfrac{-1}{3}\end{matrix}\right.\end{matrix}\right.\)
Vì \(\dfrac{-1}{3}< 1\) nên \(x=5\) thỏa mãn đề bài.
e) \(\left|x+1\right|>4\)
\(\Rightarrow\left[{}\begin{matrix}x+1>4\\x+1< 4\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x>3\\x< 3\end{matrix}\right.\)
f) \(\left|x-3\right|=\left|2x-1\right|\)
(cho thời gian suy nghĩ, mình chưa làm dạng này bao giờ)
g) \(\left|2x-1\right|-1+2x=0\)
\(\Rightarrow\left|2x-1\right|=-2x+1\)
Mà \(\left|2x-1\right|=\left|-2x+1\right|\)
\(\Rightarrow\left|-2x+1\right|=-2x+1\)
\(\Rightarrow-2x+1\ge0\)
\(\Rightarrow-2x\ge-1\)
\(\Rightarrow x\ge\dfrac{-1}{-2}=\dfrac{1}{2}\)
h) \(\left|3-2x\right|=2x-3\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x-3\ge0\\\left[{}\begin{matrix}3-2x=2x-3\\3-2x=-2x+3\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x\ge3\\\left[{}\begin{matrix}3+3=2x+2x\\3-3=-2x+2x\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ge\dfrac{3}{2}\\\left[{}\begin{matrix}6=4x\\0=0\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ge\dfrac{3}{2}\\\left[{}\begin{matrix}x=\dfrac{3}{2}\\0=0\end{matrix}\right.\end{matrix}\right.\)
Vì \(0=0\) luôn đúng nên ta có \(x=\dfrac{3}{2}\)
j) \(\left|x+1\right|+\left|x+2\right|+\left|x+3\right|+\left|x+4\right|=5x\)
(đầu hàng)
SP
3
VT
12 tháng 2 2023
\(a,x-\dfrac{3}{4}=\dfrac{1}{7}\\ x=\dfrac{1}{7}+\dfrac{3}{4}\\ x=\dfrac{25}{28}\\ b,x+\dfrac{7}{5}=\dfrac{9}{8}.\dfrac{4}{27}\\ x+\dfrac{7}{5}=\dfrac{1}{6}\\ x=\dfrac{1}{6}-\dfrac{7}{5}\\ x=\dfrac{-37}{30}\\ c,\dfrac{2}{5}-\dfrac{3}{7}=\dfrac{x}{70}\\ \dfrac{-1}{35}=\dfrac{x}{70}\\ \dfrac{-2}{70}=\dfrac{x}{70}\\ x=-2\\ d,\dfrac{2}{9}-\dfrac{7}{8}.x=1\\ \dfrac{7}{8}.x=\dfrac{2}{9}-1\\ \dfrac{7}{8}.x=\dfrac{-7}{9}\\ x=\dfrac{-7}{9}:\dfrac{7}{8}\\ x=\dfrac{-8}{9}\)
Y
12 tháng 2 2023
\(a,x-\dfrac{3}{4}=\dfrac{1}{7}\)
\(\Rightarrow x=\dfrac{1}{7}+\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{25}{28}\)
\(b,x+\dfrac{7}{5}=\dfrac{9}{8}.\dfrac{4}{27}\)
\(\Rightarrow x+\dfrac{7}{5}=\dfrac{1}{6}\)
\(\Rightarrow x=\dfrac{1}{6}-\dfrac{7}{5}\)
\(\Rightarrow x=-\dfrac{37}{30}\)
\(c,\dfrac{2}{5}-\dfrac{3}{7}=\dfrac{x}{70}\)
\(\Rightarrow\dfrac{-1}{35}=\dfrac{x}{70}\)
\(\Rightarrow35x=-70\)
\(\Rightarrow x=-2\)
\(d,\dfrac{2}{9}-\dfrac{7}{8}.x=1\)
\(\Rightarrow\dfrac{7}{8}x=\dfrac{2}{9}-1\)
\(\Rightarrow\dfrac{7}{8}x=-\dfrac{7}{9}\)
\(\Rightarrow x=-\dfrac{8}{9}\)
PT
1
VT
5 tháng 8 2017
a) ( 195 - x3 ) : 7 + 105 : 102 = 28 . 22
=> (195 - x3 ) : 7 + 1000 = 1024
=> (195 - x3 ) : 7 = 1024 - 1000 = 24
=> 195 - x3 = 24 . 7 = 168
=> x3 = 195 - 168 = 27
=> x = 3 hoặc x = - 3
Vậy : x = 3 hoặc - 3
b) 3 . ( x2 - 65 ) + 15 = 810 : 88 - 1690
=> 3 . ( x2 - 65 ) + 15 = 64 - 1 = 63
=> 3 . ( x2 - 65 ) = 63 - 15 = 48
=> x2 - 65 = 48 : 3 = 16
=> x2 = 16 + 65 = 81
=> x = 9 hoặc x = - 9
Vậy : x = 9 hoặc x = - 9
NB
2
22 tháng 6 2020
Take it easy:
2 X 2 = 42 with 4 = 2 X 2 and 2 = 2 X 2 - 2
2 X 4 = 86 with 8 = 2 X 4 and 6 = 2 X 4 - 2
6 X 3 = 1812 with 18 = 6 X 3 and 12 = 6 X 3 - 6
...
So 7 X 2 = 147 with 14 = 7 X 2 and 7 = 7 X 2 - 7
23 tháng 9 2018
\(74.\) \(\left(2x-1\right)^3\)- \(5^2\)= \(7^{18}:7^{16}\)
\(74.\)\(\left(2x-1\right)^3\)\(-5^2\)= \(7^{18-16}\)
\(74.\)\(\left(2x-1\right)^3\)\(-25\)= \(7^2\)
\(74.\)\(\left(2x-1\right)^3\)\(-25\)= \(49\)
\(74.\)\(\left(2x-1\right)^3\)= \(49+25\)
\(74.\)\(\left(2x-1\right)^3\)= \(74\)
\(\left(2x-1\right)^3\)= \(74:74\)
\(\left(2x-1\right)^3\)= \(1\)
\(\left(2x-1\right)^3=1^3\)
\(2x-1=1\)
\(2x=1+1\)
\(2x=2\)
\(x=2:2\)
\(x=1\)
Vậy x = 1
SL
6
17 tháng 8 2016
Tìm x, biết:
a. 12 + x = 122
=> x=122-12
=> x= 110
b. | x | + 4 = 8
=> /x/=8-4
=> /x/=4
=> x={4;-4}
c. 3x - 5 . 32 = 32 . 4
=> 3x=32.(4+5)
=> 3x=32.32
=> 3x=34
=> x=4
IM
17 tháng 8 2016
a)
\(12+x=122\)
=> \(x=110\)
Vậy \(x=110\)
b)
\(\left|x\right|+4=8\)
\(\Rightarrow\left|x\right|=4\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=4\\x=-4\end{array}\right.\)
Vậy x=4 ; x = - 4
c)
\(3^x-5.3^2=4.3^2\)
\(\Rightarrow3^x=3^2\left(4+5\right)\)
\(\Rightarrow3^x=3^4\)
=> x=4
Vậy x=4
MN
2
PN
28 tháng 8 2017
\(A=\left(2+\dfrac{1}{5}-\dfrac{2}{3}\right)+\left(3-\dfrac{4}{5}+\dfrac{2}{3}\right)-\left(1+\dfrac{7}{5}-\dfrac{3}{5}\right)\)
\(A=2+\dfrac{1}{5}-\dfrac{2}{3}+3-\dfrac{4}{5}+\dfrac{2}{3}-1-\dfrac{7}{5}+\dfrac{3}{5}\)
\(A=\left(2+3-1\right)+\left(\dfrac{1}{5}-\dfrac{4}{5}-\dfrac{7}{5}+\dfrac{3}{5}\right)+\left(-\dfrac{2}{3}+\dfrac{2}{3}\right)\)
\(A=4+\dfrac{-7}{5}+0\)
\(A=\dfrac{20}{5}+\dfrac{-7}{5}=\dfrac{13}{5}\)
5\(x\)\(.\)5 = 53
5\(x\) = 53 : 5
5\(x\) = 52
\(x\) = 52 : 5
\(x\) = 5
Vậy \(x=5\)
32\(.\)3\(x\) = 37
3\(x\) = 37 : 32
3\(x\) = 35
\(x\) = 35 \(:\) 3
\(x=3^4\)
\(x\) = 81
Vậy \(x=81\)