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[minhson95]

GHPT:

$$\left\{\begin{array}{l} x^2+y^2+xy+1=4y \\y(x+y)^2=2x^2+7y+2\end{array}\right.$$

Edited by minhson95, 03-02-2012 - 22:12.

[Takitori Chishikato]

GHPT:

$$\left\{\begin{array}{l} x^2+y^2+xy+1=4y \\y(x+y)^2=2x^2+7y+2\end{array}\right.$$

hpt $$\Leftrightarrow\left\{\begin{array}{l} (x^2+1)+y(x+y)=4y \\y(x+y)^2-2(x^2+1)=7y\end{array}\right.$$

NX: y=0 không TM hệ

Với y#0 chia cả 2 vế của 2 pt cho y đc

$$\left\{\begin{array}{l} \frac{x^2+1}{y}+(x+y)=4 \\y(x+y)^2-2\frac{x^2+1}{y}=7\end{array}\right.$$

Đặt $$\left\{\begin{array}{l} \frac{x^2+1}{y}=a \\x+y=b\end{array}\right.$$ giải là xong.

Edited by Takitori Chishikato, 03-02-2012 - 22:42.