Question

a, ( -5,6 + 2,9 ) x = -9,8 + x

b, x : 4 = 9 : x

c, \(\frac{x+1}{9}\)= \(\frac{7}{x-1}\)

Answer 1

câu b là dấu chia hả b

Answer 2

b)\(x:4=9:x\Leftrightarrow\frac{x}{4}=\frac{9}{x}\\ \Leftrightarrow x^2=36\\ \Leftrightarrow x^2=\left(\pm6\right)^2\\ \Rightarrow x\in\left\{6;-6\right\}\)

Vậy...

Answer 3

b) \(x:4=9:x\)

\(\Rightarrow\frac{x}{4}=\frac{9}{x}\)

\(\Rightarrow x.x=4.9\)

\(\Rightarrow x.x=36\)

\(\Rightarrow x^2=36\)

\(\Rightarrow\left[{}\begin{matrix}x=6\\x=-6\end{matrix}\right.\)

Vậy \(x\in\left\{6;-6\right\}.\)

c) \(\frac{x+1}{9}=\frac{7}{x-1}\)

\(\Rightarrow\left(x+1\right).\left(x-1\right)=7.9\)

\(\Rightarrow x^2-x+x-1=63\)

\(\Rightarrow x^2-1=63\)

\(\Rightarrow x^2=63+1\)

\(\Rightarrow x^2=64\)

\(\Rightarrow\left[{}\begin{matrix}x=8\\x=-8\end{matrix}\right.\)

Vậy \(x\in\left\{8;-8\right\}.\)

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Answer 4

c. \(\frac{x+1}{9}=\frac{7}{x-1}\Leftrightarrow\left(x+1\right)\left(x-1\right)=63\Leftrightarrow x^2-1=63\Leftrightarrow x^2=64\Leftrightarrow x=\pm8\)

a. (-5,6 + 2,9)x = -9,8 + x => -2,7x = -9,8 + x => -2,7x - x = -9,8 => -3,7x = -9,8 => x = \(\frac{-9,8}{-3,7}=\frac{98}{37}\)