Chữa đề: \(\left(2x+7\right)\sqrt{2x+7}=x^2+9x+7\)
\(\Leftrightarrow\left(2x+7\right)\sqrt{2x+7}=x^2+2x+7+7x\)
\(\Leftrightarrow x^2-2x\sqrt{2x+7}+2x+7x-7\sqrt{2x+7}=0\)
\(\Leftrightarrow\left(x-\sqrt{2x+7}\right)^2+7\left(x-\sqrt{2x+7}\right)=0\)
\(\Leftrightarrow\left(x-\sqrt{2x+7}\right)\left(x-\sqrt{2x+7}+7\right)=0\)