Question

Срочноооо
Дам 30 балів

Answer 1

1)

$x - 3y = 4 \\ 2x - y = 3 \\ \\ x = 3y + 4 \\ 2(3y + 4) - y = 3 \\ \\ 6y + 8 - y = 3 \\ 5y = 3 - 8 \\ 5y = - 5 \\ y = - 5 \div 5 \\ y = - 1 \\ \\ x = 3 \times ( - 1) + 4 \\ x = - 3 + 4 \\ x = 1$

Ответ: ( 1 ; - 1 )

2)

а)

$2x - 5y = 12 \\ 4x + 5y = 24 \\ \\ 2x + 4x = 12 + 24 \\ 6x = 36 \\ x = 36 \div 6 \\ x = 6 \\ \\ 4 \times 6 + 5y = 24 \\ 24 + 5y = 24 \\ 5y = 24 - 24 \\ 5y = 0 \\ y = 0$

Ответ: ( 6 ; 0 )

б)

$8x + 3y = 1 \\ 2x + 5y = - 21 \: \: | \times ( - 4) \\ \\ 8x + 3y = 1 \\ - 8x - 20y = 84 \\ \\ 3y - 20y = 1 + 84 \\ - 17y = 85 \\ y = 8 5\div ( - 17) \\ y = - 5 \\ \\ 2x + 5 \times ( - 5) = - 21 \\ 2x - 25 = - 21 \\ 2x = - 21 + 25 \\ 2x = 4 \\ x = 4 \div 2 \\ x = 2$

Ответ: ( 2 ; - 5 )

3)

$3x + 7y = - 4 \: \: | \times 8\\ 5x - 8y = 13 \: \: | \times 7 \\ \\ 24x + 56y = - 32 \\ 35x - 56y = 91 \\ \\ 24x + 35x = 91 - 32 \\ 59x = 59 \\ x = 59 \div 59 \\ x = 1 \\ \\ 3 \times 1 + 7y = - 4 \\ 3 + 7y = - 4 \\ 7y = - 4 - 3 \\ 7y = - 7 \\ y = - 7 \div 7 \\ y = - 1$

Ответ: ( 1 ; - 1 )