Question

Câu 1: Tìm x

\(\dfrac{x}{7}=\dfrac{6}{x+1}\)

Giúp mik gấp nhá!

Thank you very much!

Answer 1

\(\dfrac{x}{7}=\dfrac{6}{x+1}\) ĐK: x khác -1

<=> \(x\left(x+1\right)=6\cdot7\)

\(\Leftrightarrow x^2+x-42=0\)

\(\Leftrightarrow x^2-6x+7x-42=0\)

\(\Leftrightarrow x\left(x-6\right)+7\left(x-6\right)=0\)

\(\Leftrightarrow\left(x-6\right)\left(x+7\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-6=0\\x+7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-7\end{matrix}\right.\)(tm)

Vậy.....

Answer 2

Answer 3

ĐKXĐ : x \(\ne-1\)

\(\Leftrightarrow\)x (x +1) = 42

\(\Leftrightarrow\)x² + x - 42 = 0

\(\Leftrightarrow\)x² - 6x + 7x - 42 = 0

\(\Leftrightarrow\)x ( x-6) + 7(x - 6)

\(\Leftrightarrow\)(x+7)(x-6)