\(\frac{x\left(x+17\right)}{x\left(x+7\right)}=\frac{x+5}{x\left(x+7\right)}\) (ĐKXĐ: x \(\ne\) 0; x \(\ne\) -7)
\(\Leftrightarrow\) x(x + 17) = x + 5
\(\Leftrightarrow\) x2 + 17x = x + 5
\(\Leftrightarrow\) x2 + 17x - x - 5 = 0
\(\Leftrightarrow\) x2 + 16x - 5 = 0
\(\Leftrightarrow\) x2 + 16x + 64 - 69 = 0
\(\Leftrightarrow\) (x + 8)2 - 69 = 0
\(\Leftrightarrow\) (x + 8 - \(\sqrt{69}\))(x + 8 + \(\sqrt{69}\)) = 0
\(\Leftrightarrow\) x + 8 - \(\sqrt{69}\) = 0 hoặc x + 8 + \(\sqrt{69}\) = 0
\(\Leftrightarrow\) x = -8 + \(\sqrt{69}\) và x = -8 - \(\sqrt{69}\)
Vậy S = {-8 + \(\sqrt{69}\); -8 - \(\sqrt{69}\)}
Chúc bn học tốt!!
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