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1.Vì \(\frac{x}{-2}=\frac{-8}{x}\Rightarrow-2.\left(-8\right)=x.x\)
\(16=x.x\)hay \(4^2=x^2\Rightarrow x=4\)
2. Rút gọn : \(\frac{20}{28}=\frac{5}{7}=\frac{-5}{-7}\)
\(\Rightarrow x=-7\)
3. \(\frac{x}{2}-\frac{11}{5}=\frac{7}{8}\times\frac{64}{49}\)
\(\frac{x}{2}-\frac{11}{5}=\frac{8}{7}\)
Mà \(\frac{8}{7}+\frac{11}{5}=\frac{502}{35}\)
\(\Rightarrow x=\frac{234}{35}\)
1) \(\frac{x}{-2}=\frac{-8}{x}\)
\(\Rightarrow x\times x=\left(-2\right)\times\left(-8\right)\)
\(\Rightarrow x^2=16\)
\(\Rightarrow\orbr{\begin{cases}x^2=4^2\\x^2=\left(-4\right)^2\end{cases}\Rightarrow}\orbr{\begin{cases}x=4\\x=-4\end{cases}}\)
Vậy x = 4 hoặc x = -4
2) \(\frac{-5}{x}=\frac{20}{28}\)
\(\Rightarrow\frac{-5}{x}=\frac{5}{7}\)
\(\Rightarrow5\times x=\left(-5\right)\times7\)
\(\Rightarrow5\times x=-35\)
\(\Rightarrow x=\left(-35\right):5\)
\(\Rightarrow x=-7\)
Vậy x = -7
3) \(\frac{x}{2}-\frac{11}{5}=\frac{7}{8}\times\frac{64}{49}\)
\(\Rightarrow\frac{x}{2}-\frac{11}{5}=\frac{8}{7}\)
\(\Rightarrow\frac{x}{2}=\frac{8}{7}+\frac{11}{5}\)
\(\Rightarrow\frac{x}{2}=\frac{117}{35}\)
\(\Rightarrow35x=117\times2\)
\(\Rightarrow35x=234\)
\(\Rightarrow x=234:35\)
\(\Rightarrow x=\frac{234}{35}\)
Vậy \(x=\frac{234}{35}\)
4) \(\frac{x}{5}+\frac{9}{2}=\frac{6}{7}\times\frac{36}{48}\)
\(\Rightarrow\frac{x}{5}+\frac{9}{2}=\frac{9}{14}\)
\(\Rightarrow\frac{x}{5}=\frac{9}{14}-\frac{9}{2}\)
\(\Rightarrow\frac{x}{5}=\frac{-27}{7}\)
\(\Rightarrow7x=\left(-27\right)\times5\)
\(\Rightarrow7x=-135\)
\(\Rightarrow x=\left(-135\right):7\)
\(\Rightarrow x=\frac{-135}{7}\)
Vậy \(x=\frac{-135}{7}\)
5) \(\frac{3}{x-5}=\frac{-4}{x+2}\)
\(\Rightarrow\frac{3}{x-5}+\frac{4}{x+2}=0\)
\(\Rightarrow3\left(x+2\right)+4\left(x-5\right)=0\)
\(\Rightarrow3x+6+4x-20=0\)
\(\Rightarrow\left(3x+4x\right)+\left(6-20\right)=0\)
\(\Rightarrow7x-14=0\)
\(\Rightarrow7x=14\)
\(\Rightarrow x=14:7\)
\(\Rightarrow x=2\)
Vậy x = 2
_Chúc bạn học tốt_
\(5,\left(x\cdot0,5-\frac{3}{7}\right):\frac{1}{2}=1\frac{1}{7}\)
\(\Leftrightarrow x\cdot0,5:\frac{1}{2}-\frac{3}{7}:\frac{1}{2}=1\frac{1}{7}\)
\(\Leftrightarrow x-\frac{6}{7}=\frac{8}{7}\)
\(\Leftrightarrow x=2\)
\(6,x\cdot1,75=1\frac{3}{10}+45\%\)
\(\Leftrightarrow x\cdot\frac{7}{4}=\frac{13}{10}+\frac{9}{20}\)
\(\Leftrightarrow x\cdot\frac{7}{4}=\frac{7}{4}\)
\(\Leftrightarrow x=1\)
\(7,\frac{5-x}{15}+\frac{5}{12}-\frac{1}{8}=\frac{3}{8}\)
\(\Leftrightarrow\frac{5-x}{15}=\frac{3}{8}-\frac{5}{12}+\frac{1}{8}\)
\(\Leftrightarrow\frac{5-x}{15}=\frac{1}{12}\)
\(\Leftrightarrow60-12x=15\)
\(\Leftrightarrow12x=45\)
\(\Leftrightarrow x=\frac{15}{4}\)
\(8,\left|x-\frac{25}{33}\right|-\frac{3}{11}=\frac{2}{3}\)
\(\Leftrightarrow\left|\frac{x-25}{33}\right|=\frac{31}{33}\)
\(\Rightarrow\orbr{\begin{cases}x-\frac{25}{33}=\frac{31}{33}\\x-\frac{25}{33}=-\frac{31}{33}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{56}{33}\\x=-\frac{2}{11}\end{cases}}\)
\(9,-\frac{9}{8}+\frac{-3}{8}\cdot x=-\frac{1}{8}\)
\(\Leftrightarrow\frac{-9}{8}+\frac{-3}{8}\cdot x+\frac{1}{8}=0\)
\(\Leftrightarrow-1-\frac{3}{8}x=0\)
\(\Leftrightarrow\frac{3}{8}x=-1\)
\(\Rightarrow x=-\frac{8}{3}\)
Câu a:
33 ⋮ (x+ 1)
(x+ 1) ∈ Ư(33) = {-33; -11; -3; -1; 1; 3; 11}
x ∈ {-34; -12; -4; -2; 0; 2; 10}
Vậy: {-34; -12; -4; -2; 0; 2; 10}
Câu b:
x ∈ ƯC(250; 48)
250 = 2.5^3; 48 = 2^4.3
ƯCLN(250; 48) = 2
x ∈ ƯC(2) = {-2; -1}
Vậy x ∈ {-2; -1}
Câu 1:
A = -3/12 + 5/7 - (-1)/42
A = -21/84 + 60/84 + 2/84
A = 39/84 + 2/84
A = 41/84
a) \(\frac{13}{26}-\frac{1}{3}-\frac{1}{2}+\frac{7}{21}\)
\(=\frac{1}{2}-\frac{1}{3}-\frac{1}{2}+\frac{1}{3}\)
\(=\frac{1}{2}-\frac{1}{2}+\frac{1}{3}-\frac{1}{3}\)
\(=0+0\)
\(=0\)
b) \(\left(\frac{-5}{12}+\frac{6}{11}\right)+\left(\frac{7}{17}+\frac{5}{17}+\frac{5}{12}\right)\)
\(=\frac{-5}{12}+\frac{6}{11}+\frac{7}{17}+\frac{5}{17}+\frac{5}{12}\)
\(=\left(\frac{-5}{12}+\frac{5}{12}\right)+\left(\frac{7}{17}+\frac{5}{17}\right)+\frac{6}{11}\)
\(=0+\frac{12}{17}+\frac{6}{11}\)
\(=\frac{132}{187}+\frac{102}{187}\)
\(=\frac{234}{187}\)
c) \(\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{11}{16}-\frac{12}{10}\right)\)
\(=\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{11}{16}-\frac{6}{5}\right)\)
\(=\frac{13}{5}+\frac{7}{16}-\frac{11}{16}+\frac{6}{5}\)
\(=\left(\frac{13}{5}+\frac{6}{5}\right)+\left(\frac{7}{16}-\frac{11}{16}\right)\)
\(=\frac{19}{5}+\left(\frac{-4}{16}\right)\)
\(=\frac{19}{5}-\frac{1}{4}\)
\(=\frac{76}{20}-\frac{5}{20}\)
\(=\frac{71}{20}\)
d) \(-\left(\frac{3}{10}-\frac{6}{11}\right)-\left(\frac{21}{30}-\frac{5}{11}\right)\)
\(=-\left(\frac{3}{10}-\frac{6}{11}\right)-\left(\frac{7}{10}-\frac{5}{11}\right)\)
\(=-\frac{3}{10}+\frac{6}{11}-\frac{7}{10}+\frac{5}{11}\)
\(=
\left(-\frac{3}{10}-\frac{7}{10}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)\)
\(=\frac{-10}{10}+\frac{11}{11}\)
\(=-1+1\)
\(=0\)
1.
A=\(\frac{-5x+-5y+-5z}{21}=\frac{-5\left(x+y+z\right)}{21}=\frac{-5}{21}.x+y+z\)
A= -z+z=0
<p style="padding: 10000000000000000px;" class="alert success"></p>
A. \(\frac{3}{4}\) x \(\frac{8}{9}\)x \(\frac{15}{16}\)x .... x \(\frac{899}{900}\)
= \(\frac{1.3}{2^2}\) x \(\frac{2.4}{3^3}\)x \(\frac{3.5}{4^2}\)x ... x \(\frac{29.31}{30^2}\)
= \(\left(\frac{1.2.3...29}{2.3.4...30}\right).\left(\frac{3.4.5...31}{2.3.4...30}\right)\)
= \(\frac{1}{30}.\frac{31}{2}\)= \(\frac{31}{60}\)
B.
\(\frac{1}{3}+\frac{3}{8}-\frac{7}{12}=\frac{8}{24}+\frac{9}{24}-\frac{14}{24}=\frac{8+9-14}{24}=\frac{3}{24}=\frac{1}{8}\)
Bài 2:
a; -8/9 và -7/9
Vì 8/9 > 7/9
- 8/9 < - 7/9 (nhân cả hai vế của bất đẳng thức với một số âm thì dấu của bất đẳng thức đổi chiều.
* x/7 = -6/21
=> x = -6.7 : 21
=> x = -2
* x/-2 = -8/x
=> x.x = -8.(-2) = 16
=> x^2 = 16
=> x = 4 hoặc x = -4
\(\frac{-2}{7}\)= \(\frac{-6}{21}\)
\(\frac{4}{-2}\)= \(\frac{-8}{4}\)
Học tốt ^-^
Đầu bài *2 và *3 là 3/x-5 = -4/x+2 đúng không? Nếu đúng thì bạn tham khảo bài dưới mk làm nha
3/x-5 = -4/x+2
=>3.(x+2) = -4.(x-5)
=> 3x+6 = -4x + 20
=> 3x+4x = 20-6
=> 7x = 14
=> x = 2