Question

{3x+3y=-1 și { 3X+Y=1

Answer 1

y=1-3x inlocuind in prima
3x+3(1-3x)=-1
3x+3-9x=-1
-6x=-4
x=2/3
y=1-3x=1-3.2/3=1-2=-1

x=2/3
y=-1

Answer 2

$\left\{\begin{matrix} 3x + 3y = - 1 \: | \times ( - 1) \\ 3x + y = 1\end{matrix}\right.$

$\left\{\begin{matrix} - 3x - 3y = 1\\ 3x + y = 1\end{matrix}\right.$

$- 3x + 3x - 3y + y = 1 + 1$

$- 3y + y = 2$

$- 2y = 2 \: | \div ( - 2)$

$y = - 1$

$3x + y = 1$

$3x + ( - 1) = 1$

$3x - 1 = 1$

$3x = 1 + 1$

$3x = 2$

$x = \frac{2}{3}$