Question

\(x-\sqrt{2x-5}=4\)

Answer 1

\(x-\sqrt{2x-5}=4\)

ĐK: \(\left\{{}\begin{matrix}2x-5\ge0\\x\ge4\end{matrix}\right.\)\(\Leftrightarrow x\ge4\)

\(x-\sqrt{2x-5}=4\Leftrightarrow\sqrt{2x-5}=x-4\)

Ta bình phương 2 vế:

\(2x-5=\left(x-4\right)^2\)

\(\Leftrightarrow2x-5=x^2-8x+16\)

\(\Leftrightarrow x^2-10x+21=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=7\left(nhận\right)\\x=3\left(loại\right)\end{matrix}\right.\)

Answer 2

refer

https://hoc247.net/hoi-dap/toan-9/giai-phuong-trinh-x-can-2x-5-4-faq446795.html