Р прямоугольника = (а + b) * 2
а = Р : 2 - b
64 : 2 - 14 = 18 (см)
Ответ: а = 18 см
1) 27,2*3:17=4,8 кг масса сурьмы в сплаве
2) 27,2+4,8=32 кг масса сплава.
Ответ 32 кг
А) [a*b^(1/2) / (a^(1/2) + b^(1/2)) + b*a^(1/2) / (a^(1/2) - b^(1/2))]*a^(-1/2)*b^(-1/2) =
= [a*b^(1/2)*(a^(1/2)-b^(1/2)) + b*a^(1/2)*(a^(1/2)+b^(1/2))]/(a - b)*a^(-1/2)*b^(-1/2) =
= a^(1/2)*b^(1/2)*[a^(1/2)*(a^(1/2)-b^(1/2)) + b^(1/2)*(a^(1/2)+b^(1/2))] /
/ (a - b)*a^(-1/2)*b^(-1/2) =
= [a^(1/2)*(a^(1/2)-b^(1/2)) + b^(1/2)*(a^(1/2)+b^(1/2))] / (a - b) =
= (a - a^(1/2)*b^(1/2) + a^(1/2)*b^(1/2) + b) / (a - b) = (a + b)/(a - b)
б) 1/a^(-1/4) = a^(1/4), поэтому
[(a^(1/4) - b^(1/4))^2 + 1 / (a^(1/4) + b^(1/4))^2] : [(a^(1/2) + b^(1/2)) / (a - b)] =
= [(a^(1/4) - b^(1/4))^2*(a^(1/4) + b^(1/4))^2 + 1] / (a^(1/4) + b^(1/4))^2 :
: (a^(1/2) + b^(1/2)) / [(a^(1/2) + b^(1/2))*(a^(1/2) - b^(1/2))] =
= [(a^(1/2) - b^(1/2))^2 + 1] / (a^(1/4) + b^(1/4))^2 : 1 / (a^(1/2) - b^(1/2)) =
= [(a^(1/2) - b^(1/2))^2 + 1] / (a^(1/4) + b^(1/4))^2 * (a^(1/2) - b^(1/2))
Больше не сокращается, наверное, какая-то ошибка в задании
Ну если брать теоретически, то в 16 раз должна уменьшится цена.
0,8(3) = 5/6
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Пусть х = 0,8333 ..., тогда
10х = 8,333 ...
100х = 83,333...
100х - 10х = 83,333 - 8,333
90х = 75
х = 75/90
х = 5/6 (дробь 75/90 сократили на 15)
Ответ: 5/6.