\(3x^2+y^2+2x-2y=1\)

\(\Leftrightarrow\left(2x^2+2xy\right)+x^2-2xy+y^2+2\left(x-y\right)+1=2\)

\(\Leftrightarrow A+\left(x-y+1\right)^2=2\)

 \(A>0=\left(x-y+1\right)^2< 2\)

A nguyên \(\orbr{\begin{cases}\left(x-y+1\right)^2=0\\\left(x-y+1\right)^2=1\end{cases}\Rightarrow\orbr{\begin{cases}A=2\\A=1\end{cases}}}\)

Đơn giản 

ta có \(a+x=b;a-x=b\)

Suy ra \(a+x+a-x=2b\)

\(\Leftrightarrow2a=2b\)

\(\Leftrightarrow a=b\)

Thay b bằng a ta có

\(a+x=a\)

\(\Leftrightarrow x=a-a=0\)

Vậy a=b

và x=0

Find the word which has a different sound in the part underlined.

1.A.class B.answer C.fat D.fast

2.A.great B.teacher C.stream D.meat

3.A.dear B.wear C.nearby D.appear

4.A.washes B.passes C.lakes D.couches

sai bét