Б) Второе из задуманных чисел равно произведению числа аи числа 3,3, а пер- вое - произведению числа b и числа 4,7. Найдите разность между первым и вторым числами.
Х --- скорость пешехода (х+9) --- скорость велосипедиста (2 / х) --- время пешехода (2 / (х+9)) --- время велосипедиста, оно на 12 мин = 12/60 часа меньше времени пешехода... (2/(х+9)) + (1/5) = 2/х (10+х+9) / ((х+9)*5) = 2/х х(19+х) = 10(х+9) x^2 + 19x - 10x - 90 = 0 x^2 + 9x - 90 = 0 D=81+4*90 = 9*(9+40) = 21^2 x1 = (-9-21)/2 ---отрицательная скорость не имеет смысла))) х = (-9+21)/2 = 12/2 = 6 км/час --- скорость пешехода, 6+9 = 15 км/час скорость велосипедиста ПРОВЕРКА: велосипедист 2 км проедет за 2/15 часа пешеход пройдет 2 км за 2/6 = 1/3 часа (1/3) - (2/15) = (5-2)/15 = 3/15 = 1/5 часа = 12 минут
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Must Waste More Time...
(х+9) --- скорость велосипедиста
(2 / х) --- время пешехода
(2 / (х+9)) --- время велосипедиста, оно на 12 мин = 12/60 часа меньше
времени пешехода...
(2/(х+9)) + (1/5) = 2/х
(10+х+9) / ((х+9)*5) = 2/х
х(19+х) = 10(х+9)
x^2 + 19x - 10x - 90 = 0
x^2 + 9x - 90 = 0
D=81+4*90 = 9*(9+40) = 21^2
x1 = (-9-21)/2 ---отрицательная скорость не имеет смысла)))
х = (-9+21)/2 = 12/2 = 6 км/час --- скорость пешехода,
6+9 = 15 км/час скорость велосипедиста
ПРОВЕРКА:
велосипедист 2 км проедет за 2/15 часа
пешеход пройдет 2 км за 2/6 = 1/3 часа
(1/3) - (2/15) = (5-2)/15 = 3/15 = 1/5 часа = 12 минут