1 reply to this topic

[congdaoduy9a]

Giải hệ pt : 

$\left\{\begin{matrix} (x+6y+3)\sqrt{xy+3y}=(8y+3x+9)y & & \\ \sqrt{-x^{2}+8x-24y+417}=(y+3)\sqrt{y-1}+3y+17 & & \end{matrix}\right.$

 

[phan huong]

Giải hệ pt : 

$\left\{\begin{matrix} (x+6y+3)\sqrt{xy+3y}=(8y+3x+9)y & & \\ \sqrt{-x^{2}+8x-24y+417}=(y+3)\sqrt{y-1}+3y+17 & & \end{matrix}\right.$

Từ pt (1)$\Rightarrow \sqrt{y}(2\sqrt{y}-\sqrt{x+3})(4y-\sqrt{y}\sqrt{x+3}+x+3)=0$

=>$2\sqrt{y}=\sqrt{x+3}\Leftrightarrow 4y=x+3$

thế vào (2) ..........

Edited by phan huong, 05-04-2015 - 21:10.