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AM
2
DH
26 tháng 6 2017
Với mọi giá trị của \(x\in R\) ta có:
\(\left|x+1\right|\ge0;\left|x+1,2\right|\ge0;\left|x+1,3\right|\ge0;\left|x+1,4\right|\ge0\)
\(\Rightarrow\left|x+1\right|+\left|x+1,2\right|+\left|x+1,3\right|+\left|x+1,4\right|\ge0\)
mà \(\left|x+1\right|+\left|x+1,2\right|+\left|x+1,3\right|+\left|x+1,4\right|=5x\)
nên \(5x\ge0\Rightarrow x\ge0\)
\(\Rightarrow\left\{{}\begin{matrix}\left|x+1\right|=x+1\\\left|x+1,2\right|=x+1,2\\\left|x+1,3\right|=x+1,3\\\left|x+1,4\right|=x+1,4\end{matrix}\right.\)
\(\Rightarrow x+1+x+1,2+x+1,3+x+1,4=5x\)
\(\Rightarrow4x+4,9=5x\Rightarrow x=4,9\)
Chúc bạn học tốt!!!
26 tháng 6 2017
\(\left|x+1\right|\ge0\) \(\left|x+1,2\right|\ge0\)
\(\left|x+1,3\right|\ge0\) \(\left|x+1,4\right|\ge0\)
\(\Leftrightarrow\left|x+1\right|+\left|x+1,2\right|+\left|x+1,3\right|+\left|x+1,4\right|\ge0\)
\(\Leftrightarrow x+1+x+1,2+x=1,3+x+1,4=5x\)
\(4x+4,9=5x\)
\(\Leftrightarrow x=4,9\)
BK
4
9 tháng 8 2019
= 34,8: ( 1,8+ 4) - 1,9
=34,8: 2, 2- 1,9
= 348/ 10x 10/ 22- 19/10
=174/ 5x 5/ 11- 19/10
= 174/11- 19/11
= 174- 19/11
=155/11
LG
23 tháng 7 2017
a) \(\left|3,5-x\right|=1,3\)
\(\Rightarrow\left[{}\begin{matrix}3,5-x=1,3\\3,5-x=-1,3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=3,5-1,3\\x=3,5+1,3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=2,2\\x=4,8\end{matrix}\right.\)
b) \(1,6-\left|x-0,2\right|=0,4\)
\(\Rightarrow\left|x-0,2\right|=1,2\)
\(\Rightarrow\left[{}\begin{matrix}x-0,2=1,2\\x-0,2=-1,2\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1,2+0,2\\x=-1,2+0,2\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1,4\\x=-1\end{matrix}\right.\)
23 tháng 7 2017
\(\left|3,5-x\right|=1,3\)
\(\Rightarrow\left[{}\begin{matrix}3,5-x=1,3\Rightarrow x=2,2\\3,5-x=-1,3\Rightarrow x=4,8\end{matrix}\right.\)
\(1,6-\left|x-0,2\right|=0,4\)
\(\Rightarrow\left|x-0,2\right|=1,2\)
\(\Rightarrow\left[{}\begin{matrix}x-0,2=1,2\Rightarrow x=1,4\\x-0,2=-1,2\Rightarrow x=-1\end{matrix}\right.\)
\(\left|x-1,5\right|+\left|2,5-x\right|=0\)
\(\left\{{}\begin{matrix}\left|x-1,5\right|\ge0\\\left|2,5-x\right|\ge0\end{matrix}\right.\)
\(\Rightarrow\left|x-1,5\right|+\left|2,5-x\right|\ge0\)
Dấu "=" xảy ra khi:
\(\left\{{}\begin{matrix}\left|x-1,5\right|=0\Rightarrow x=1,5\\\left|2,5-x\right|=0\Rightarrow x=2,5\end{matrix}\right.\)
\(1,5\ne2,5\Rightarrow x\in\varnothing\)
DT
5
DH
8 tháng 8 2019
a, \(\left(x-158\right):6=20\)
\(x-158=20.6\)
\(x-158=120\)
\(x=120+158\)
\(x=278\)
~~~Hok tốt~~~
8 tháng 8 2019
a) \(\left(x-158\right):6=20\)
\(\Leftrightarrow x-158=\frac{20}{6}=\frac{10}{3}\)
\(\Leftrightarrow x=\frac{10}{3}+158\)
\(\Leftrightarrow x=\frac{484}{3}\)
Vậy : \(x=\frac{484}{3}\)
b) \(x-1,25.4=2,5\)
\(\Leftrightarrow x-5=2,5\)
\(\Leftrightarrow x=2,5+5\)
\(\Leftrightarrow x=7,5\)
Vậy : \(x=7,5\)
c) \(x+0,25=\frac{43}{4}-\frac{18}{5}\)
\(\Leftrightarrow x+\frac{1}{4}=\frac{143}{20}\)
\(\Leftrightarrow x=\frac{143}{20}-\frac{1}{4}\)
\(\Leftrightarrow x=\frac{69}{10}\)
Vậy : \(x=\frac{69}{10}\)
SL
2
PA
15 tháng 7 2016
a.
\(1,25\times4-x=2,5\)
\(5-x=2,5\)
\(x=5-2,5\)
\(x=2,5\)
b.
\(\left(158-x\right)\div7=20\)
\(158-x=20\times7\)
\(158-x=140\)
\(x=158-140\)
\(x=18\)
c.
\(x-0,25=\frac{43}{4}-\frac{18}{5}\)
\(x-\frac{1}{4}=\frac{43}{4}-\frac{18}{5}\)
\(x=\frac{43}{4}-\frac{18}{5}+\frac{1}{4}\)
\(x=\left(\frac{43}{4}+\frac{1}{4}\right)-\frac{18}{5}\)
\(x=\frac{44}{4}-\frac{18}{5}\)
\(x=11-\frac{18}{5}\)
\(x=\frac{37}{5}\)
15 tháng 7 2016
a. 1,25 × 4 - x = 2,5
5- x= 2,5
x= 5-2,5
x=2,5
b.(158- x) :7= 20
158- x= 20x7
158 -x= 140
x=158- 140
x=18
c. x- 0,25= \(\frac{43}{4}+\frac{18}{5}\)
x- 0,25=14,35
x= 14,35+ 0,25
x=14,6
E
3
30 tháng 4 2019
a, 0,25 - x = -0,75
x = 0,25 - -0,75
x = 1
b,x:(-3)= -\(\frac{2}{3}\)
x = -\(\frac{2}{3}\) >< -3
x = -2
c,(1,1.x-9).\(\frac{2}{5}\)=80%
1,1 >< x -9 = \(\frac{80}{100}\) : \(\frac{2}{5}\)
1,1 >< x -9 = 2
1,1 >< x = 2 + 9
1,1 >< x = 11
x =11 : 1,1
x = 10
d,2.x-30%.x=-1,7
x >< (2-0,3)=1,7
x >< 0,7 = 1,7
x = 1,7 : 0,7
x = 2.42857142857
8 tháng 6 2019
Bài 1:
\(a,22\frac{1}{2}.\frac{7}{9}+50\%-1,25\)
=\(\frac{45}{2}.\frac{7}{9}+\frac{1}{2}-\frac{5}{4}\)
=\(\frac{35}{2}+\frac{1}{2}-\frac{5}{4}\)
=\(\frac{70}{4}+\frac{2}{4}-\frac{5}{4}\)
=\(\frac{67}{4}\)
\(b,1,4.\frac{15}{49}-\left(\frac{4}{5}+\frac{2}{3}\right):2\frac{1}{5}\)
=\(\frac{7}{5}.\frac{15}{49}-\left(\frac{12}{15}+\frac{10}{15}\right):\frac{11}{5}\)
=\(\frac{3}{7}-\frac{22}{15}.\frac{5}{11}\)
=\(\frac{3}{7}-\frac{2}{3}\)
=\(-\frac{5}{21}\)
\(c,125\%.\left(-\frac{1}{2}\right)^2:\left(1\frac{5}{6}-1,6\right)+2016^0\)
=\(\frac{5}{4}.\frac{1}{4}:\left(\frac{11}{6}-\frac{8}{5}\right)+1\)
=\(\frac{5}{16}:\frac{7}{30}+1\)
=\(\frac{131}{56}\)
\(d,1,4.\frac{15}{49}-\left(20\%+\frac{2}{3}\right):2\frac{1}{5}\)
=\(\frac{7}{5}.\frac{15}{49}-\left(\frac{1}{5}+\frac{2}{3}\right):\frac{11}{5}\)
=\(\frac{3}{7}-\frac{13}{15}:\frac{11}{5}\)
=\(\frac{3}{7}-\frac{13}{33}\)
=\(\frac{8}{231}\)
Bài đ làm giống hệt như bài c
Bài 2 :
\(a,\left|\frac{3}{4}.x-\frac{1}{2}\right|=\frac{1}{4}\)
=>\(\left[{}\begin{matrix}\frac{3}{4}.x-\frac{1}{2}=\frac{1}{4}\\\frac{3}{4}.x-\frac{1}{2}=-\frac{1}{4}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}\frac{3}{4}.x=\frac{1}{4}+\frac{1}{2}=\frac{3}{4}\\\frac{3}{4}.x=-\frac{1}{4}+\frac{1}{2}=\frac{1}{4}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=\frac{3}{4}:\frac{3}{4}=1\\x=\frac{1}{4}:\frac{3}{4}=\frac{1}{3}\end{matrix}\right.\)
Vậy x ∈{1;\(\frac{1}{3}\)}
\(b,\frac{5}{3}.x-\frac{2}{5}.x=\frac{19}{10}\)
=>\(\frac{19}{15}.x=\frac{19}{10}\)
=>\(x=\frac{19}{10}:\frac{19}{15}=\frac{3}{2}\)
Vậy x ∈ {\(\frac{3}{2}\)}
c,\(\left|2.x-\frac{1}{3}\right|=\frac{2}{9}\)
=>\(\left[{}\begin{matrix}2.x-\frac{1}{3}=\frac{2}{9}\\2.x-\frac{1}{3}=-\frac{2}{9}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}2.x=\frac{2}{9}+\frac{1}{3}=\frac{5}{9}\\2.x=-\frac{2}{9}+\frac{1}{3}=\frac{1}{9}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=\frac{5}{9}:2=\frac{5}{18}\\x=\frac{1}{9}:2=\frac{1}{18}\end{matrix}\right.\)
Vậy x∈{\(\frac{5}{18};\frac{1}{18}\)}
\(d,x-30\%.x=-1\frac{1}{5}\)
=\(70\%x=-\frac{6}{5}\)
=\(\frac{7}{10}.x=-\frac{6}{5}\)
=>\(x=-\frac{6}{5}:\frac{7}{10}=-\frac{12}{7}\)
Vậy x∈{\(-\frac{12}{7}\)}
TG
8 tháng 6 2019
Bài 2
a/
\(\Rightarrow\left[{}\begin{matrix}\frac{3}{4}.x-\frac{1}{2}=\frac{1}{4}\\\frac{3}{4}.x-\frac{1}{2}=-\frac{1}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\frac{3}{4}.x=\frac{1}{4}+\frac{1}{2}\\\frac{3}{4}.x=-\frac{1}{4}+\frac{1}{2}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\frac{3}{4}.x=\frac{3}{4}\\\frac{3}{4}.x=\frac{1}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\frac{3}{4}:\frac{3}{4}\\x=\frac{1}{4}:\frac{3}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=\frac{1}{3}\end{matrix}\right.\)
Vậy \(x=1\) hoặc \(x=\frac{1}{3}\)
b/ Đặt x làm thừa số chung rồi tính như bình thường
c/ Tương tự câu a
d/ Tương tự câu b
23 tháng 7 2023
2x3,12x1,25x0,25x10=2x3,12x(1,25:0,25x10)
=2x3,12 x50
=100x3,12=312
5.76576