(*) Xét xy = 0 => x = 0 hoặc y = 0 

   (+) x =  0 thay vào pt (1) => y^2 + 1 = 0 ( vn) 

   (+) y = 0 ( TT )

(*) xét xy khác 0 

Chia cả hai vế pt (1) cho xy ta có :

\(\frac{\left(x^2+1\right)\left(y^2+1\right)}{xy}+8=0\Leftrightarrow\frac{x^2+1}{x}\cdot\frac{y^2+1}{y}+8=0\)

Đặt \(\frac{x}{x^2+1}=a;\frac{y}{y^2+1}=b\) ta có hpt 

\(\int^{\frac{1}{a}\cdot\frac{1}{b}+8=0}_{a+b=-\frac{1}{4}}\Leftrightarrow\int^{\frac{1}{ab}=-8}_{a+b=-\frac{1}{4}}\Leftrightarrow\int^{ab=-\frac{1}{8}}_{a+b=-\frac{1}{4}}\)

=>a ; b là nghiệm của pt \(X^2+\frac{1}{4}X-\frac{1}{8}=0\Leftrightarrow8X^2+2X-1=0\)

=> a ; b => tìm đc x ; y 

\(\left\{{}\begin{matrix}4x+3x=-6\\\dfrac{x+3y}{3}-\dfrac{y-2}{5}=1\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}7x=-6\\\dfrac{5\left(x+3y\right)-3\left(y-2\right)}{15}=1\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x=-\dfrac{6}{7}\\5x+15y-3y+6=15\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x=-\dfrac{6}{7}\\12y=9-5x=9+5\cdot\dfrac{6}{7}=9+\dfrac{30}{7}=\dfrac{93}{7}\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x=-\dfrac{6}{7}\\y=\dfrac{93}{7\cdot12}=\dfrac{93}{84}=\dfrac{31}{28}\end{matrix}\right.\)

5x-2>2(x+3)\(\Leftrightarrow\)5x-2>2x+6

\(\Leftrightarrow\) 5x-2x>6+2

\(\Leftrightarrow\)3x>8

\(\Leftrightarrow\)x>\(\dfrac{8}{3}\)

Chúc bn học tốt❤

\(\hept{\begin{cases}3x-y=2m+3\\x+2y=3m+1\end{cases}}\Leftrightarrow\hept{\begin{cases}6x-2y=4m+6\\x+2y=3m+1\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}x=m+1\\y=m\end{cases}}\)khi đó: \(^{x^2+y^2=5\Leftrightarrow2m^2+2m+1=5\Leftrightarrow2m^2+2m-4=0\Leftrightarrow\orbr{\begin{cases}m=1\\m=-2\end{cases}}}\)

2( x - 1 ) - 5 = 3( 5 - 3x)

2x - 2 - 5 = 15 - 9x

2x - 7 = 15 - 9x

2x + 9x = 15 + 7

11x = 22

x = 2

Vậy x = 2 

\(2\left(x-1\right)-5=3\left(5-3x\right)\)

\(\Leftrightarrow2x-2-5=15-9x\)

\(\Leftrightarrow2x-\left(2+5\right)=15-9x\)

\(\Leftrightarrow2x-7=15-9x\)

\(\Leftrightarrow2x+9x=15+7\)

\(\Leftrightarrow11x=22\)

\(\Leftrightarrow x=22\div11\)

\(\Leftrightarrow x=2\)

\(\text{Vậy }x=2\)

2( x - 1 ) - 5 = 3( 5 - 3x)

    2x - 2 - 5 = 15 - 9x

         2x - 7 = 15 - 9x

      2x + 9x = 15 + 7

            11x = 22

                x = 2