Предмет: Алгебра, автор: Milanifi

СРОЧНО! Даю 50 баллов. Алгебра, 7 класс.

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Ответы

Автор ответа: volna7

Відповідь:

Швидкість мотоцикліста 25 км./год., а швидкість велосипедиста 11 км./год.

Пояснення:

Позначимо швидкість мотоцикліста як Х, а швидкість велосипедиста як У. Маємо систему рівняннь:

3Х + 3У = 108 ( 1 )

2Х - У = 39 ( 2 )

Розділимо обидві частини рівняння ( 1 ) на 3 і зробимо вираз У крізь Х:

Х + У = 36

У = 36 - Х ( 3 )

Підставимо У з рівняння ( 3 ) в ріаняння ( 2 ), отримаємо:

2Х - 36 + Х = 39

3Х = 75

Х = 25 км./год.

Підставимо Х = 25 до рівняння ( 3 ), отримаємо:

У = 36 - 25 = 11 км./год.

Перевірка:

Підставимо значення Х та У до рівняннь ( 1 ) та ( 2 ), отримаємо:

( 1 )

3 × 25 + 3 × 11 = 108

75 + 33 = 108

108 = 108

( 2 )

2 × 25 - 11 = 39

50 - 11 = 39

39 = 39

Все вірно.

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