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Câu 1a:
75% - 1 1/2 + 0,5 : 5/12 - (-1/2)^2
= 0,75 - 1,5 + 0,5 x 12/5 - 0,25
= (0,75 - 0,25) - 1,5 + 1,2
= 0,5 - 1,5 + 1,2
= - 1 + 1,2
= 0,2
Bài 1b:
(5/7.0,6 - 5: 3 1/2). (40% - 1,4).(-2)^3
= (3/7 - 5 x 2/7).(0,4 - 1,4).8
= - 1.(-1).8
= 8
\(a,\left[\frac{4}{5}+\frac{2}{3}\right]:\frac{1}{5}-1,4\cdot\left[\frac{-5}{7}\right]^2\)
\(=\left[\frac{4\cdot3}{15}+\frac{2\cdot5}{15}\right]:\frac{1}{5}-1,4\cdot\frac{-5}{7}\cdot\frac{-5}{7}\)
\(=\left[\frac{12}{15}+\frac{10}{15}\right]:\frac{1}{5}-\frac{14}{10}\cdot\frac{25}{49}\)
\(=\frac{22}{15}:\frac{1}{5}-\frac{7}{5}\cdot\frac{25}{49}\)
\(=\frac{22}{15}\cdot\frac{5}{1}-\frac{7}{5}\cdot\frac{25}{49}\)
\(=\frac{22\cdot5}{15\cdot1}-\frac{7\cdot25}{5\cdot49}=\frac{22\cdot1}{3\cdot1}-\frac{1\cdot5}{1\cdot7}=\frac{22}{3}-\frac{5}{7}\)
= ...
Tự tính
Bài 2 : \(a,3-\left|\frac{1}{2}x-\frac{1}{3}\right|=\frac{1}{2}\)
\(\Rightarrow\left|\frac{1}{2}x-\frac{1}{3}\right|=\frac{1}{2}+3\)
\(\Rightarrow\left|\frac{1}{2}x-\frac{1}{3}\right|=\frac{7}{2}\)
\(\Rightarrow\hept{\begin{cases}\frac{1}{2}x-\frac{1}{3}=\frac{7}{2}\\\frac{1}{2}x-\frac{1}{3}=-\frac{7}{2}\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{23}{3}\\x=\frac{-19}{3}\end{cases}}\)
Vậy \(x\in\left\{\frac{23}{3};\frac{-19}{3}\right\}\)
b, \(0,6-160\%< x\le3\frac{2}{3}:\frac{22}{18}\)
\(\Rightarrow0,6-\frac{160}{100}< x\le\frac{11}{3}:\frac{22}{18}\)
\(\Rightarrow0,6-\frac{8}{5}< x\le\frac{11}{3}\cdot\frac{18}{22}\)
\(\Rightarrow0,6-1,6< x\le3\)
\(\Rightarrow-1< x\le3\)
\(\Rightarrow x\in\left\{0;1;2;3\right\}\)
Câu a:
- \(\frac12\)(3 - 2\(x\)) - 7 = 5 - \(\frac13\)(\(x\) - \(\frac45\))
- \(\frac32\) + \(x\) - 7 = 5 - \(\frac13x\) + \(\frac{4}{15}\)
\(x\) + \(\frac13x\) = 5 + \(\frac{4}{15}\) + 7 + \(\frac32\)
(1 + \(\frac13\))\(x\) = \(\frac{150}{30}\) + \(\frac{8}{30}\) + \(\frac{210}{30}\) + \(\frac{45}{30}\)
\(\frac43x\) = \(\frac{158}{30}\) + \(\frac{210}{30}\) + \(\frac{45}{30}\)
\(\frac43x\) = \(\frac{368}{30}\) + \(\frac{45}{30}\)
\(\frac43x\) = \(\frac{413}{30}\)
\(x\) = \(\frac{413}{30}\) : \(\frac43\)
\(x\) = \(\frac{413}{40}\)
Vậy \(x=\frac{413}{40}\)
Câu b:
(5 - 3x/2) : - 1 3/8 = - 7 1/3
(5 - 3x/2) : (-11/8) = - 22/3
5 - 3x/2 = - 22/3 x (-11/8)
5 - 3x/2 = 121/12
3x/2 = 5 - 121/12
3x/2 = - 61/12
x = - 61/12 : 3/2
x = -61/18
Vậy x = - 61/18
a, \(\frac{\left(2^3.5.7\right)\left(5^2.7^3\right)}{\left(2.5.7^2\right)^2}\)\(=\frac{2^3.5.7.5^2.7^3}{2^2.5^2.7^4}=\frac{2^3.5^3.7^4}{2^2.5^2.7^4}=10\)
b, \(\frac{4}{77}+\frac{4}{165}+\frac{4}{285}\)
\(=\frac{4}{7.11}+\frac{4}{11.15}+\frac{4}{15.19}\)
\(=\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+\frac{1}{15}-\frac{1}{19}\)
\(=\frac{1}{7}-\frac{1}{19}\)
\(=\frac{19}{133}-\frac{7}{133}=\frac{12}{133}\)
Bài 2:
\(a,\left(x+\frac{2}{3}\right).\frac{-3}{5}+\frac{4}{7}=1\frac{4}{7}.x\)
\(\Rightarrow\frac{-3}{5}x+\frac{-2}{5}+\frac{4}{7}=\frac{11}{7}.y\)
\(\Rightarrow\frac{-3}{5}x+\frac{6}{35}=\frac{11}{7}.y\)
Từ đây làm nốt
b, \(\left|5x-2\right|\le0\)
\(\Rightarrow\left|5x\right|\le2\)( x \(\ge0\))
Mà không có số x nào nhân với 5 bé hơn hoặc bằng 2
\(\Rightarrow\)x không có giá trị thỏa mãn
c đề bài sai, chỉ tìm x chứ làm gì có y
d, \(\left(x-3\right).\left(2y+1\right)=7\)
TH1:
x - 3 = 1
x = 1 + 3
x = 4
2y + 1 = 7
2y = 7 - 1 = 6
y = 6 : 2 = 3
TH2:
x - 3 = 7
x = 7 + 3 = 10
2y + 1 = 1
2y = 1 - 1 = 0
y = 0 : 2 = 0
TH3:
x - 3 = -1
x = -1 + 3
x = 2
2y+ 1 = -7
2y = -7 - 1 = -8
y = (-8) : 2 = -4
TH4:
x - 3 = -7
x = -7 + 3
x = -4
2y + 1 = -1
2y = (-1) - 1
2y = -2
y = (-2) : 2 = -1
Vậy ......
a) \(\frac{x}{5}=\frac{2}{3}\)
\(\Rightarrow\)\(x=\frac{2.5}{3}=\frac{10}{3}\)
Vậy....
b) \(\frac{x+3}{15}=\frac{1}{5}\)
\(\Leftrightarrow\)\(5\left(x+3\right)=15\)
\(\Leftrightarrow\)\(x+3=3\)
\(\Leftrightarrow\)\(x=0\)
Vậy....
Bài 1:
Câu a:
2/3.(x -5/6) + 1/4 = 22/9
2/3.(x -5/6) = 22/9 - 1/4
2/3.(x -5/6) = 79/36
x - 5/6 = 79/36 : 2/3
x - 5/6 = 79/24
x = 5/6 + 79/24
x = 33/8
Vậy x = 33/8
a) -0,6 . x - 7/3 = 5,4 (sửa dấu phẩy thành dấu nhân)
=> \(-\frac{3}{5}x-\frac{7}{3}=\frac{27}{5}\)
=> \(-\frac{3}{5}x=\frac{27}{5}+\frac{7}{3}=\frac{116}{15}\)
=> \(x=\frac{116}{15}:\left(-\frac{3}{5}\right)=\frac{116}{15}\cdot\left(-\frac{5}{3}\right)=-\frac{116}{9}\)
b) 2,8 : \(\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\)
=> \(\frac{1}{5}-3x=2,8:1\frac{2}{5}\)
=> \(\frac{1}{5}-3x=\frac{14}{5}:\frac{7}{5}=\frac{14}{5}\cdot\frac{5}{7}=2\)
=> 3x = \(\frac{1}{5}-2=-\frac{9}{5}\)
=> \(x=\left(-\frac{9}{5}\right):3=\left(-\frac{9}{5}\right)\cdot\frac{1}{3}=-\frac{3}{5}\)
Nên sửa lại đề câu a đi nhá :))