Question

Нужно решить только 1261 первую и вторую систему

Answer 1

1)

$2x - 3y + 1 + (x - y + 5) = 0 \\ 5x + 7y - (8x + y + 1) = 0 \\ \\ 2x - 3y + 1 + x - y + 5 = 0 \\ 5x + 7y - 8x - y - 1 = 0 \\ \\ 3x - 4y + 6 = 0 \\ - 3x + 6y - 1 = 0</p<p$

Складываем

$2y + 5 = 0 \\ 2y = - 5 \\ y = - 5 \div 2 \\ y = - 2.5 \\ \\ 3x - 4y + 6 = 0 \\ 3x - 4 \times ( - 2.5) + 6 = 0 \\ 3x + 10 + 6 = 0 \\ 3x + 16 = 0 \\ 3x = - 16 \\ x = - 16 \div 3 \\ x = - 5 \frac{1}{3} \\ \\ otvet \: ( - 5 \frac{1}{3} \: ; \: - 2.5)$

2)

$7x + 9y - 14 + y - 5x - 11 + 3 = 0 \\ 11x + y - 9 + 4y - 9x - 7 = 0 \\ \\ 2x + 10y - 22 = 0 \\ 2x + 5y - 16 = 0 \: \: | \times ( - 1)\\ \\ 2x + 10y - 22 = 0 \\ - 2x - 5y + 16 = 0$

Складываем

$5y - 6 = 0 \\ 5y = 6 \\ y = 6 \div 5 \\ y = 1.2 \\ \\ 2x + 10y - 22 = 0 \\ 2x + 10 \times 1.2 - 22 = 0 \\ 2x + 12 - 22 = 0 \\ 2x - 10 = 0 \\ 2x = 10 \\ x = 10 \div 2 \\ x = 5 \\ \\ otvet \: (5 \: ; \: 1.2)$