2 replies to this topic

[SweetCandy11]

4/ $\left\{\begin{matrix} \sqrt{x-2y+6}=8x^4-8x^2+3 & \\ \frac{5+\sqrt{x-2y+6}}{1+\sqrt{x-2y+6}}=2x^2 & \end{matrix}\right.$

 

5/ $\left\{\begin{matrix} y+xy^2=-6x^2 & \\ 1+x^3y=19x^3 & \end{matrix}\right.$

 

6/ $\left\{\begin{matrix} \sqrt{11+x-y}-\sqrt{y-x}=1 & & \\ 7\sqrt{y-x}+6y-26x=3 & & \end{matrix}\right.$

[Tran Nho Duc]

6/ $\left\{\begin{matrix} \sqrt{11+x-y}-\sqrt{y-x}=1 & & \\ 7\sqrt{y-x}+6y-26x=3 & & \end{matrix}\right.$

$\sqrt{11+x-y}-\sqrt{y-x}=1\Leftrightarrow \frac{11+2x-2y}{\sqrt{11+x-y}+\sqrt{y-x}}=1
\Rightarrow \left\{\begin{matrix} \sqrt{11+x-y}-\sqrt{y-x}=1\\ \sqrt{11+x-y}+\sqrt{y-x}=11+2x-2y \end{matrix}\right. \Rightarrow \sqrt{y-x}=5-(y-x)\Leftrightarrow \sqrt{y-x}= \frac{-1\pm \sqrt{21}}{2}$

 

Edited by Tran Nho Duc, 13-12-2015 - 13:00.

[An Infinitesimal]

 

4/ $\left\{\begin{matrix} \sqrt{x-2y+6}=8x^4-8x^2+3 & \\ \frac{5+\sqrt{x-2y+6}}{1+\sqrt{x-2y+6}}=2x^2 & \end{matrix}\right.$

 

5/ $\left\{\begin{matrix} y+xy^2=-6x^2 & \\ 1+x^3y=19x^3 & \end{matrix}\right.$

 

6/ $\left\{\begin{matrix} \sqrt{11+x-y}-\sqrt{y-x}=1 & & \\ 7\sqrt{y-x}+6y-26x=3 & & \end{matrix}\right.$

Bài 4+6) Đặt $u=\sqrt{x-2y+6}+1$, ta có hệ

$\left\{\begin{matrix} u=2(2x^2-1)^2 & \\ \frac{4}{u}=2x^2-1 & \end{matrix}\right.$

Phương pháp thế xử lý cả 2.

 

Bài 5: Khả năng gõ đề sai rất cao!