Question

tìm x biết:

x+4/20 =5/x+4

Answer 1

\(\frac{x+4}{20}=\frac{5}{x+4}\)

\(\Rightarrow\left(x+4\right)^2=5.20\)

\(\Rightarrow\left(x+4\right)^2=100\)

\(\Rightarrow\left(x+4\right)^2=\pm10^2\)

\(\Rightarrow\left[{}\begin{matrix}x+4=10\\x+4=-10\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=10-4\\x=-10-4\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=6\\x=-14\end{matrix}\right.\)

Vậy \(x=6\) hoặc \(x=-14\)

Answer 2

\(\frac{x+4}{20}=\frac{5}{x+4}\)

\(\Rightarrow\left(x+4\right).\left(x+4\right)=5.20\)

\(\Rightarrow\left(x+4\right).\left(x+4\right)=100\)

\(\Rightarrow\left(x+4\right)^2=100\)

\(\Rightarrow x+4=\pm10.\)

\(\Rightarrow\left[{}\begin{matrix}x+4=10\\x+4=-10\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=10-4\\x=\left(-10\right)-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=6\\x=-14\end{matrix}\right.\)

Vậy \(x\in\left\{6;-14\right\}.\)

Chúc bạn học tốt!

Answer 3

\(\frac{x+4}{20}=\frac{5}{x+4}\\ \Leftrightarrow\left(x+4\right)^2=100\\ \Leftrightarrow\left(x+4\right)^2=\left(\pm10\right)^2\\ \Rightarrow\left\{{}\begin{matrix}x+4=10\\x+4=-10\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=6\\x=-14\end{matrix}\right.\)

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