Конкурс исполнителей проводится в 3 дня. всего заявлено 80 выступлений-по одному от каждой страны. впервый день 20 выступлений, остальные разделены поровну между оставшимися днями. порядок выступления определяется жребием. какого вероятность, что высткпление представителя россии состоится в 3 день конкурса?

1)80-20=60 -на 2

2)60: 30=30 - последующие 2

всего-80

30-в 3 день

р==0,375 

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АнонимМатематика07 февраля 16:29

Разложите на множители: а)100а⁴-1/9 b2 б)9х²-(х-1)² в)х³+у⁶

ответ или решение1

Белов Лев

Чтобы разложить выражения на множители, воспользуемся формулами сокращённого умножения, а именно формулой разности квадратов a^2 - b^2 = (a - b) * (a + b) и формулой суммы кубов а^3 + b^3 = (a + b) * (a^2 - ab + b^2):

1) 100a^4 - 1/9b^2 = (10a^2 - 1/3b) * (10a^2 + 1/3b);

a^2 = 100a^4;

a = √100a^4;

a = 10a^2;

b^2 = 1/9b^2;

b = 1/3b.

2) 9x^2 - (x - 1)^2 = (3x - (x - 1)) * (3x + (x - 1)) = (3x - x + 1) * (3x + x - 1) = (2x + 1) * (4x - 1);

3) x^3 + y^6 = (x + y^2) * (x^2 - xy^2 + y^4);

a^3 = x^3;

a = x;

b^3 = y^6;

b = y^2;

ab = x * y^2 = xy^2.

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