ответ: власна шв.човна 9км/год , швидкість течії 3 км/год .
Пошаговое объяснение:
Нехай х км/год - швидкість за течією , а у км/год - шв. проти течії
Система :
{ 2x + 3y = 42 , │X 2
{ 3x + 2y = 48 ; │ X ( - 3 )
{4x + 6y = 84 ,
{- 9x - 6y = - 144 ;
- 5x = - 60 ;
x = 12 .
Із 2-го рівняння 1-ої системи 3*12 + 2у = 48 ; 2у = 48 - 36 ; 2у = 12 ; у =6.
Отже , шв. за течією 12 км/год , а шв. проти течії 6 км/год .
Швидкість течії : ( 12 - 6 ) : 2 = 3 ( км/год ) , а власна шв.човна
12 - 3 = 9 ( км/год ) .
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Пошаговое объяснение:
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S=60х8=480см2
2) ответ: 2дм=20см
S=20х9=180см2