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HT
25 tháng 7 2017
\(=\frac{16}{5}.\frac{15}{16}-\left(\frac{3}{4}+\frac{2}{7}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{21}{28}+\frac{8}{28}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{29}{28}\right).\left(\frac{-28}{29}\right)\)
\(=3-\left(-1\right)\)
\(=4\)
b) \(=\left(\frac{1}{4}+\frac{25}{2}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3}{8}-\frac{1}{12}\right)\right)\)
\(=\left(\frac{4}{16}+\frac{200}{16}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3.3}{2.3.4}-\frac{2}{2.3.4}\right)\right)\)
\(=\left(\frac{199}{16}\right):\left(12-\frac{7}{12}:\left(\frac{9}{24}-\frac{2}{24}\right)\right)\)
\(=\frac{199}{16}:\left(12-\frac{7}{12}.\frac{24}{7}\right)\)
\(=\frac{199}{16}:\left(12-2\right)\)
\(=\frac{199}{16}:10\)
\(=\frac{199}{160}\)
c) \(\left(\frac{-3}{5}+\frac{5}{11}\right):\frac{-3}{7}+\left(\frac{-2}{5}+\frac{6}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-33}{55}+\frac{25}{55}\right):\frac{-3}{7}+\left(\frac{4}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-8}{55}\right).\frac{-7}{3}+\frac{4}{5}.\frac{-7}{3}\)
\(\frac{-7}{3}\left(\frac{-8}{55}+\frac{4}{5}\right)\)
\(\frac{-7}{3}.\frac{36}{55}=\frac{-84}{55}\)
13 tháng 7 2016
\(\frac{2}{\left(x-1\right)\left(x-3\right)}+\frac{5}{\left(x-3\right)\left(x-8\right)}+\frac{12}{\left(x-8\right)\left(x-20\right)}-\frac{1}{x-20}=-\frac{3}{4}\)
\(=\frac{1}{x-1}-\frac{1}{x-3}+\frac{1}{x-3}-\frac{1}{x-8}+\frac{1}{x-8}-\frac{1}{x-20}-\frac{1}{x-20}=-\frac{3}{4}\)
\(=\frac{1}{x-1}-\frac{2}{x-20}=-\frac{3}{4}\)
\(\frac{-x-18}{\left(x-1\right)\left(x-20\right)}=-\frac{3}{4}\)
\(\frac{-x-18}{x^2-21x+20}=\frac{-3}{4}\)
\(\frac{x+18}{x^2-21x+20}=\frac{3}{4}\)
\(4\left(x+18\right)=3\left(x^2-21x+20\right)\)
\(4x+72=3x^2-63x+60\)
\(3x^2-63x-4x=72-60\)
\(3x^2-67x=12\)
\(x\left(2x-67\right)=12\)
\(\Rightarrow x;2x-67\inƯ\left(12\right)=\left\{-12;-6;-4;-3;-2;-1;1;2;3;4;6;12\right\}\)
Mà 2x - 67 lẻ.
Ta có bảng sau:
| 2x-67 | 2x | x | (2x - 67 ) . x |
| -3 | 64 | 32 | -96 ( loại) |
| -1 | 66 | 33 | -33 ( loại ) |
| 1 | 68 | 34 | 34 ( loại) |
| 3 | 70 | 35 | 105(loại) |
Do đó không có \(x\)thỏa mãn.
21 tháng 6 2018
a) \(\frac{x-1}{8}=\frac{5}{4}\)
\(\frac{x-1}{8}=\frac{10}{8}\)
\(\Leftrightarrow x-1=10\)
\(x=10+1\)
\(x=11\)
vậy x =11
b)\(\frac{6}{2x-1}=\frac{12}{-8}\)
\(\frac{6}{2x-1}=\frac{6}{-4}\)
\(\Leftrightarrow2x-1=-4\)
\(2x=-4+1\)
\(2x=-3\)
\(x=\frac{-3}{2}\)
vậy \(x=\frac{-3}{2}\)
c) \(\frac{2x-5}{-12}=\frac{-6}{9}\)
\(\frac{2x-5}{-12}=\frac{-2}{3}\)
\(\frac{2x-5}{-12}=\frac{8}{-12}\)
\(\Leftrightarrow2x-5=8\)
\(2x=8+5\)
\(2x=13\)
\(x=\frac{13}{2}\)
vậy \(x=\frac{13}{2}\)
Q
20 tháng 12 2017
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{x}{3}=\frac{y}{5}=\frac{x+y}{3+5}=\frac{-24}{8}=-3\)
\(\frac{x}{3}=-3\Rightarrow x=\left(-3\right).3=-9\)
\(\frac{y}{5}=-3\Rightarrow y=\left(-3\right).5=-15\)
b) \(\frac{x}{5}=\frac{y}{8}=\frac{x-y}{5-8}=\frac{15}{-3}=-5\)
\(\frac{x}{5}=-5\Rightarrow x=\left(-5\right).5=-25\)
\(\frac{y}{8}=-5\Rightarrow y=\left(-5\right).8=-40\)
c) 7x=4y <=> x/4=y/7
\(\frac{x}{4}=\frac{y}{7}=\frac{x+y}{4+7}=\frac{12}{11}\)
\(\frac{x}{4}=\frac{12}{11}\Rightarrow x=\frac{12}{11}.4=\frac{48}{11}\)
\(\frac{y}{7}=\frac{12}{11}\Rightarrow y=\frac{12}{11}.7=\frac{84}{11}\)
d) tt câu c
e) x/5=y/8;z/3=y/12 <=> x/60=y/96=z/24
\(\frac{x}{60}=\frac{y}{96}=\frac{z}{24}=\frac{4x}{4.60}=\frac{2y}{2.96}=\frac{z}{24}=\frac{2y+z-4x}{192+24-240}=\frac{30}{-24}=\frac{-5}{4}\)
\(\frac{x}{60}=\frac{-5}{4}\) => x=-5/4.60=-75
y/96=-5/4 => y=-5/4.96=-120
z/24=-5/4 => z=-5/4.24=-30
25 tháng 1 2017
a) \(\frac{x+1}{3}=\frac{x-2}{4}\)
=> (x+1).4 = (x - 2) . 3
=> 4x + 4 = 3x - 6
=> 4x - 3x = - 6 - 4
=> x = - 10
b) \(\frac{x-6}{7}+\frac{x-7}{8}+\frac{x-8}{9}=\frac{x-9}{10}+\frac{x-10}{11}+\frac{x-11}{12}\)
\(\Rightarrow\left(\frac{x-6}{7}+1\right)+\left(\frac{x-7}{8}+1\right)+\left(\frac{x-8}{9}+1\right)=\left(\frac{x-9}{10}+1\right)+\left(\frac{x-10}{11}+1\right)+\left(\frac{x-11}{12}+1\right)\)
\(\Rightarrow\frac{x+1}{7}+\frac{x+1}{8}+\frac{x+1}{9}=\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}\)
\(\Rightarrow\frac{x+1}{7}+\frac{x+1}{8}+\frac{x+1}{9}-\frac{x+1}{10}-\frac{x+1}{11}-\frac{x+1}{12}\) = 0
\(\Rightarrow\left(x+1\right).\left(\frac{1}{7}+\frac{1}{8}+\frac{1}{9}-\frac{1}{10}-\frac{1}{11}-\frac{1}{12}\right)\)
Vì \(\frac{1}{7}+\frac{1}{8}+\frac{1}{9}-\frac{1}{10}-\frac{1}{11}-\frac{1}{12}\ne0\) nên x + 1 =0
=> x = -1
c) Xem lại đề
NT
0
19 tháng 6 2016
<=>\(\frac{8}{3}< x+\frac{1}{5}< \frac{499}{56}\)
<=>\(\begin{cases}\frac{8}{3}< x+\frac{1}{5}\\x+\frac{1}{5}< \frac{499}{56}\end{cases}\)
<=> \(\begin{cases}x>\frac{37}{15}\\x< \frac{2439}{280}\end{cases}\)
=> x\(\in\left(\frac{37}{15};\frac{2439}{280}\right)\)
kb vs mk r mk giải cho nek
\(\frac{x}{12}=\frac{3}{8}\)
=> x.8 = 3.12
=> x.8 = 36
=> x = 36/8 = 9/2