Câu 1 chắc chắn đề sai
Câu 2:
ĐKXĐ: ...
Đặt \(\sqrt{\frac{4x+9}{28}}=a+\frac{1}{2}\Rightarrow\left(a+\frac{1}{2}\right)^2=\frac{4x+9}{28}\)
Ta được hệ:
\(\left\{{}\begin{matrix}7x^2+7x=a+\frac{1}{2}\\\left(a+\frac{1}{2}\right)^2=\frac{4x+9}{28}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}14x^2+14x=2a+1\\14a^2+14a=2x+1\end{matrix}\right.\)
\(\Rightarrow14x^2-14a^2+14x-14a=2a-2x\)
\(\Leftrightarrow7\left(x-a\right)\left(x+a\right)+8\left(x-a\right)=0\)
\(\Leftrightarrow\left(x-a\right)\left(7x+7a+8\right)=0\)
\(\Leftrightarrow...\)
