$=\mathop {\lim }\limits_{x \to 1}\frac{\sqrt{x^3+5x^2+7x+3}-\sqrt{9x^3+7x^2}-(x-1)\sqrt{9x+7}}{x-1}$
$=\mathop {\lim }\limits_{x \to 1}\frac{\frac{(x-1)(-8x^2-10x-3)}{(x+1)\sqrt{x+3}+x\sqrt{9x+7}}-(x-1)\sqrt{9x+7}}{x-1}$$=\mathop {\lim }\limits_{x \to 1}\left ( \frac{-8x^2-10x-3}{(x+1)\sqrt{x+3}+x\sqrt{9x+7}}-\sqrt{9x+7}\right )$
$=\frac{-53}{8}$
Ktra nếu thấy đúng kq Click V dùm mk nhé ! Thanks