Chứng minh : A=1+2+2^2+2^3+2^4+...+2^29 chia hết cho7
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\(a.\frac{2}{5}-x=-\frac{3}{10}\Leftrightarrow x=\frac{2}{5}+\frac{3}{10}=\frac{7}{10}\)
\(b.x-\frac{1}{15}=\frac{3}{2}\Leftrightarrow x=\frac{1}{15}+\frac{3}{2}=\frac{47}{30}\)
\(c.\frac{3}{8}-x=-\frac{5}{12}\Leftrightarrow x=\frac{3}{8}+\frac{5}{12}=\frac{19}{24}\)
\(d.\frac{11}{13}-\left(\frac{5}{42}-x\right)=0\Leftrightarrow x=\frac{5}{42}-\frac{11}{13}=-\frac{397}{546}\)
\(e.\frac{2}{3}x+\frac{5}{7}=\frac{3}{10}\Leftrightarrow\frac{2}{3}x=\frac{3}{10}-\frac{5}{7}=-\frac{29}{70}\Leftrightarrow x=-\frac{29}{70}:\frac{2}{3}=-\frac{87}{140}\)
\(g.-5x\left(x-\frac{5}{4}\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\x-\frac{5}{4}=0\Leftrightarrow x=\frac{5}{4}\end{cases}}\)
\(h.\left|x+\frac{3}{4}\right|=\frac{1}{2}\Leftrightarrow\orbr{\begin{cases}x+\frac{3}{4}=\frac{1}{2}\\x+\frac{3}{4}=-\frac{1}{2}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-\frac{1}{4}\\x=-\frac{5}{4}\end{cases}}}\)
\(k.-\frac{21}{13}x+\frac{1}{3}=-\frac{2}{3}\Leftrightarrow-\frac{21}{13}x=-\frac{1}{3}-\frac{2}{3}=-1\Leftrightarrow x=\frac{13}{21}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
giải
th1
2x+3=5
2x =2
x = 1
th2
2x+3=-5
2x =-5 -3
2x = -8
x = -4
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
a) \(|2x-5|=-4\)
=> ko có giá trị x nào thoả mãn
b) \(\frac{1}{3}-|\frac{5}{4}-2x|=\frac{1}{4}\)
=> \(|\frac{5}{4}-2x|=\frac{1}{12}\)
=> \(\orbr{\begin{cases}\frac{5}{4}-2x=\frac{1}{12}\\\frac{5}{4}-2x=-\frac{1}{12}\end{cases}}\)
=> \(\orbr{\begin{cases}2x=\frac{7}{6}\\2x=\frac{4}{3}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{7}{12}\\x=\frac{2}{3}\end{cases}}\)
Bài 2 :
a) \(2|2x-3|=\frac{1}{2}\)
=> \(|2x-3|=\frac{1}{4}\)
=> \(\orbr{\begin{cases}2x-3=\frac{1}{4}\\2x-3=-\frac{1}{4}\end{cases}}\)
=> \(\orbr{\begin{cases}2x=\frac{13}{4}\\2x=\frac{11}{4}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{13}{8}\\x=\frac{11}{8}\end{cases}}\)
b) \(7,5-3|5-2x|=-4,5\)
=> \(3|5-2x|=12\)
=>\(|5-2x|=4\)
=> \(\orbr{\begin{cases}5-2x=4\\5-2x=-4\end{cases}}\)
=> \(\orbr{\begin{cases}2x=1\\2x=9\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{9}{2}\end{cases}}\)
Bài 3 :
a) \(2|3x-1|+1=5\)
=> \(2|3x-1|=4\)
=> \(|3x-1|=2\)
=> \(\orbr{\begin{cases}3x-1=2\\3x-1=-2\end{cases}}\)
=> \(\orbr{\begin{cases}3x=3\\3x=-1\end{cases}}\)
=> \(\orbr{\begin{cases}x=1\\x=-\frac{1}{3}\end{cases}}\)
b) \(|\frac{x}{2}-1|=3\)
=> \(\orbr{\begin{cases}\frac{x}{2}-1=3\\\frac{x}{2}-1=-3\end{cases}}\)
=> \(\orbr{\begin{cases}\frac{x}{2}=4\\\frac{x}{2}=-2\end{cases}}\)
=> \(\orbr{\begin{cases}x=8\\x=-4\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{x}{3}=\frac{9}{x^2}\)
=> \(x^3=27\)
=> \(x^3=3^3\)
=> \(x=3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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2 mũ 13 -2 nhé
cả lời giải bạn ơi