ĐK:$x\geq -3$;$y\geq 1$;...pt(1)$\Leftrightarrow$$\left[ {(x+3)+6y} \right]\sqrt{y(x+3)}=\left[ {8y+3(x+3)} \right]y$ (1')
Đặt $\begin{cases}\sqrt{x+3}=a \\ \sqrt{y} =b\end{cases}$;$a\geq 0;b\geq 1$
(1') tt:$(a^{2}+6b^{2})ab=(8b^{2}+3a^{2})b^{2}$
$\Leftrightarrow $$b(a-2b)(a^{3}+5ab+4b^{2})$=0
$\Rightarrow$$a=2b$ $\Rightarrow$$ x=4y-3$
(2)tt$\sqrt{-16y^{2}+32y+384}=(y+3)\sqrt{y-1}+3y+17$(3)
Xét thấy:$\sqrt{-16y^{2}+32y+384}=\sqrt{-16(y-1)^{2}+400}\leq20$(4)
$(y+3)\sqrt{y-1}+3y+17\geq20( y\geq1)$(5)
(3)$\Leftrightarrow$(4)&(5) xra dấu''=''$\Leftrightarrow$y=1
$\Rightarrow$x=1(t/m đk)
KL:...