Вправи: 1209 (1)

1209. 1) Розв’яжіть систему рівнянь:

3(y – x)–4 = –7y, 3y – 3x – 4 = –7y, 10y – 3x = 4, 3x = 10y – 4,

5(x + y) + 9 = 8x; 5x + 5y + 9 = 8x; 5y – 2x = –9; 5y – 3x = –9;

x = 10y-43, x = 10y-43, x = 10y-43, x = 10y-43,

5y – 3 ∙ 10y-43 = –9; 5y – 10y + 4 = –9; –5y = –13; y = 135,

x = 10 • 135 - 43, x = 223,

y = 135, y = 135.

Відповідь: (223; 135)

2) x2 + y = 5│∙ 2, x + 2y = 10, x = 10 – 2y, x = 10 – 2y

x – y3 = 3│∙3; 3x – y = 9; 3(10 – 2y) – y = 9; 30–6y – y = 9;

x = 10 – 2y, x = 10 – 2y, x = 4,

–7y = –21; y = 3; y = 3.

Відповідь:(4; 3).