Question

ПОЖАЛУЙСТА НАДО ЗДЕЛАТЬ ВСЕ ЗАДАНИЕ ПОД ЦЫФРОЙ 1
НА ЛИСТОЧКЕ ЗДЕЛАТЬ!!!​

Answer 1

А)

$\displaystyle\bf\\ + \left \{ {{3x - 2y = 7} \atop {7x + 2y = 23 }} \right. \\ \\ 3x + 7x = 7 + 23 \\ 10x = 30 \\ x = 30 \div 10 \\ x = 3 \\ \\ 3 \times 3 - 2y = 7 \\ 9 - 2y = 7 \\ 2y = 9 - 7 \\ 2y = 2 \\ y = 2 \div 2 \\ y = 1$

Ответ: ( 3 ; 1 )

Б)

$\displaystyle\bf\\\left \{ {{x + 4y = 1} \atop {3x - 2y = 17 \: \: | \times 2 }} \right. \\ \displaystyle\bf\\ + \left \{ {{x + 4y = 1} \atop {6x - 4y = 34 }} \right. \\ \\ x + 6x = 1 + 34 \\ 7x = 35 \\ x = 35 \div 7 \\ x = 5 \\ \\ 5 + 4y = 1 \\ 4y = 1 - 5 \\ 4y = - 4 \\ y = - 4 \div 4 \\ y = - 1$

Ответ: ( 5 ; - 1 )

В)

$\displaystyle\bf\\\left \{ {{0.2x - 0.7y = 2 \: \: | \times 30} \atop {0.5x + 0.3y = 25.5 \: \: | \times 70 }} \right. \\ \displaystyle\bf\\ + \left \{ {{6x - 21y = 60} \atop {35x + 21y = 1785 }} \right. \\ \\ 6x + 35x = 60 + 1785 \\ 41x = 1845 \\ x = 1845 \div 41 \\ x = 45 \\ \\ 0.5 \times 45 + 0.3y = 25.5 \\ 22.5 + 0.3y = 25.5 \\ 0.3y = 25.5 - 22.5 \\ 0.3y = 3 \\ y = 3 \div 0.3 \\ y = 10$

Ответ: ( 45 ; 10 )