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\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
=> \(x\left(-x\right)=\left(-9\right)\frac{4}{49}\)
=> \(-x^2\)\(=\frac{-36}{49}\)
=> \(x^2=\frac{36}{49}\)
=> \(x=\frac{6}{7}\)
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
\(\Rightarrow x^2=\left(-9\right)\left(\frac{-4}{49}\right)\)
\(\Rightarrow x^2=\frac{36}{49}\)
\(\Rightarrow x=\sqrt{\frac{36}{49}}\)
\(\Rightarrow x=\frac{\sqrt{36}}{\sqrt{49}}\)
\(\Rightarrow x=\frac{\sqrt{6^2}}{\sqrt{7^2}}\)
\(\Rightarrow x=\frac{6}{7}\)
vay \(x=\frac{6}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
không có giá trị tồn tại x :)
Vì :
9.4/49=x.(-x)
=> 0.7346938776 = x.(-x)
Nhưng đề phải có thí dụ như x thuộc tập hợp số hữu tỉ hoặc gì đó :)
\(\frac{9}{x}=\frac{-x}{\frac{4}{49}}\Rightarrow x.\left(-x\right)=9.\frac{4}{49}\)\(\Leftrightarrow-x^2=\frac{36}{49}\Rightarrow x^2=-\frac{36}{49}\)
vậy đề bài vô lý
![](https://rs.olm.vn/images/avt/0.png?1311)
a) x/-27=-3/x
suy ra: x.x=-3.(-27)
suy ra: x^2=81. Suy ra: x^2=9^2 hoặc (-9)^2
suy ra: x=9 hoặc x=-9
Vậy x=9 hoặc x=-9
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{1}{4}+\frac{1}{3}:2x=-5\)
\(\frac{1}{3}:2x=\frac{-21}{4}\)
\(2x=\frac{-4}{63}\)
\(x=\frac{2}{63}\)
b) \(\left(3x-\frac{1}{4}\right)\left(x+\frac{1}{2}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}3x-\frac{1}{4}=0\\x+\frac{1}{2}=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{1}{12}\\x=\frac{-1}{2}\end{cases}}\)
Vậy.........
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
\(\Rightarrow x^2=-9.\left(\frac{-4}{49}\right)\)
\(\Rightarrow x^2=\frac{36}{49}\)
\(\Rightarrow x=\sqrt{\frac{36}{49}}\)
\(\Rightarrow x=\sqrt{\frac{6^2}{7^2}}\)
\(\Rightarrow x=\sqrt{\left(\frac{6}{7}\right)^2}\)
\(\Rightarrow x=\frac{6}{7}\)
vay \(x=\frac{6}{7}\)
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
-9 x\(\frac{4}{49}\)=\(x\times\left(-x\right)\)
\(-\frac{36}{49}\)= -2x
\(\Rightarrow\)2x=\(\frac{36}{49}\)( cùng bớt dấu âm của 2 vế)
x=\(\frac{36}{49}:2\)
x=\(\frac{18}{49}\)
vậy x = \(\frac{18}{49}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\Leftrightarrow-x.x=-9.\frac{4}{49}\Leftrightarrow-x^2=-\frac{36}{49}\)
\(\Leftrightarrow x^2=\frac{36}{49}\Leftrightarrow\sqrt{x}=\sqrt{\frac{36}{49}}\Leftrightarrow x=\hept{\begin{cases}\frac{6}{7}\\-\frac{6}{7}\end{cases}}\)
(Nhớ k cho mình với nhé!)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\)
\(\Rightarrow x.x=\left(-9\right).\left(-\frac{4}{49}\right)\)
\(\Rightarrow x^2=\frac{36}{49}\)
\(\Rightarrow x^2=\hept{\begin{cases}\left(\frac{6}{7}\right)^2\\\left(-\frac{6}{7}\right)^2\end{cases}}\)
\(\Rightarrow x=\hept{\begin{cases}+\frac{6}{7}\\-\frac{6}{7}\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a) \(\frac{x}{-27}=\frac{-3}{x}\Leftrightarrow-\frac{x}{27}=-\frac{3}{x}\Leftrightarrow-x.x=\left(-27\right).\left(-3\right)\Leftrightarrow-x^2=-81\Leftrightarrow\orbr{\begin{cases}x=9\\x=-9\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=9\\x=-9\end{cases}}\)
b) \(\frac{-9}{x}=\frac{-x}{\frac{4}{49}}\Leftrightarrow-\frac{9}{x}=-\frac{49x}{4}\Leftrightarrow-9.4=-x.49x\Leftrightarrow-36=-49x^2\Leftrightarrow\orbr{\begin{cases}x=\frac{6}{7}\\x=-\frac{6}{7}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{6}{7}\\x=-\frac{6}{7}\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1
A= \(\frac{81^{10}.3^{17}}{27^{10}.9^{13}}\)
= \(\frac{\left(3^4\right)^{10}.3^{17}}{\left(3^3\right)^{10}.\left(3^2\right)^{13}}\)
= \(\frac{3^{40}.3^{17}}{3^{30}.3^{26}}\)
= \(\frac{3^{57}}{3^{56}}\)= 3
\(\frac{x}{7}\)= \(\frac{-12}{49}\)
=> 49x = (-12) x 7
=> 49x = -84
=> x= \(\frac{-12}{7}\)
\(-\frac{9}{x}=-\frac{x}{\frac{9}{49}}\)
<=> x.x = \(-9.\left(-\frac{9}{49}\right)\)
<=> x2 = \(\frac{81}{49}\) = \(\left(\frac{9}{7}\right)^2\)= \(\left(-\frac{9}{7}\right)^2\)
=> x = + \(\frac{9}{7}\)