Question

1.Rezolvati sistemul prin metoda subsitutiei :
2x-3y =8
3x+y=1
2metoda reducerii:
3x+2y=-7
4x+3y=-10
Dau coroana!
Urgent!

Answer 1

$1)\left\{\begin{matrix} 2x - 3y = 8\\ 3x + y = 1\end{matrix}\right.$

$3x + y = 1$

$y = 1 - 3x$

$2x - 3y = 8$

$2x - 3(1 - 3x) = 8$

$2x - 3 + 9x = 8$

$2x + 9x = 8 + 3$

$11x = 11 \: | \div 11$

$x = 1$

$y = 1 - 3x$

$y = 1 - 3 \times 1$

$y = 1 - 3$

$y = - 2$

$2)\left\{\begin{matrix} 3x + 2y = - 7 \: | \times 3\\ 4x + 3y = - 10 \: | \times ( - 2)\end{matrix}\right.$

$\left\{\begin{matrix} 9x + 6y = - 21\\ - 8x - 6y = 20\end{matrix}\right.$

$9x - 8x + 6y - 6y = - 21 + 20$

$x = - 1$

$9x + 6y = - 21$

$9 \times ( - 1) + 6y = - 21$

$- 9 + 6y = - 21$

$6y = - 21 + 9$

$6y = - 12 \: | \div 6$

$y = - 2$