А) 5a * 3a = 15a^2 B) 4ab * a^2 = 4a^3b C) - 4a^2b * ( - 3ab^2) = 12 a^3 b^3 D) 7x^2 * (-9x) = 63x3

Докажем тождества:

А) 5 * a * 3 * a = 15 * a^2;

15 * a * a = 15 * a^2;

15 * a^2 = 15 * a^2;

Верно;

B) 4 * a * b * a^2 = 4 * a^3 * b;

4 * a^3 * b = 4 * a^3 * b;

Верно;

C) - 4 * a^2 * b * (-3 * a * b^2) = 12 * a^3 * b^3;

4 * a^2 * b * 3 * a * b^2 = 12 * a^3 * b^3;

12 * a^3 * b^3 = 12 * a^3 * b^3;

Верно;

D) 7 * x^2 * (-9 * x) = 63 * x^3;

-7 * 9 * x^3 = 63 * x^3;

-63 * x^3 = 63 * x^3;

Неверно.