1) $(5x^2 - 6x^4 + 48x^6 - 12x^3) : x = \frac{x(5x - 6x^3 + 48x^5 - 12x^2)}{x} = 5x - 6x^3 + 48x^5 - 12x^2$;
2) $(5x^2 - 6x^4 + 48x^6 - 12x^3) : x^2 = \frac{x^2(5 - 6x^2 + 48x^4 - 12x)}{x^2} = 5 - 6x^2 + 48x^4 - 12x$;
3) $(5x^2 - 6x^4 + 48x^6 - 12x^3) : 10x^2 = \frac{10x^2(0,5 - 0,6x^2 + 4,8x^4 - 1,2x)}{10x^2} = 0,5 - 0,6x^2 + 4,8x^4 - 1,2x$.
Ответ: $x; x^2; 10x^2$.

1) $(14x^6 - 28x + 7x^5 + 84x^4 - 56x^8) : x = \frac{x(14x^5 - 28 + 7x^4 + 84x^3 - 56x^7)}{x} = 14x^5 - 28 + 7x^4 + 84x^3 - 56x^7$;
2) $(14x^6 - 28x + 7x^5 + 84x^4 - 56x^8) : 7x = \frac{7x(2x^5 - 4 + x^4 + 12x^3 - 8x^7)}{7x} = 2x^5 - 4 + x^4 + 12x^3 - 8x^7$;
3) $(14x^6 - 28x + 7x^5 + 84x^4 - 56x^8) : 10x = \frac{10x(1,4x^5 - 2,8 + 0,7x^4 + 8,4x^3 - 5,6x^7)}{10x} = 1,4x^5 - 2,8 + 0,7x^4 + 8,4x^3 - 5,6x^7$.
Ответ: x; 7x; 10x.

1) $(15a^2b^3 + 25a^4b^2 - 30a^6b^3 - 75a^4b^7) : ab = \frac{ab(15ab^2 + 25a^3b - 30a^5b^2 - 75a^3b^6)}{ab} = 15ab^2 + 25a^3b - 30a^5b^2 - 75a^3b^6$;
2) $(15a^2b^3 + 25a^4b^2 - 30a^6b^3 - 75a^4b^7) : 5ab = \frac{5ab(3ab^2 + 5a^3b - 6a^5b^2 - 15a^3b^6)}{5ab} = 3ab^2 + 5a^3b - 6a^5b^2 - 15a^3b^6$;
3) $(15a^2b^3 + 25a^4b^2 - 30a^6b^3 - 75a^4b^7) : 5a^2b^2 = \frac{5a^2b^2(3b + 5a^2 - 6a^4b - 15a^2b^5)}{5a^2b^2} = 3b + 5a^2 - 6a^4b - 15a^2b^5$.
Ответ: $ab; 5ab; 5a^2b^2$.

1) $(45m^6n^2 + 30m^3n^5 + 60m^4n^3 - 90m^4n^5) : mn = \frac{mn(45m^5n + 30m^2n^4 + 60m^3n^2 - 90m^3n^4)}{mn} = 45m^5n + 30m^2n^4 + 60m^3n^2 - 90m^3n^4$;
2) $(45m^6n^2 + 30m^3n^5 + 60m^4n^3 - 90m^4n^5) : 15mn = \frac{15mn(3m^5n + 2m^2n^4 + 4m^3n^2 - 6m^3n^4)}{15mn} = 3m^5n + 2m^2n^4 + 4m^3n^2 - 6m^3n^4$;
3) $(45m^6n^2 + 30m^3n^5 + 60m^4n^3 - 90m^4n^5) : 15m^2n^2 = \frac{15m^2n^2(3m^4 + 2mn^3 + 4m^2n - 6m^2n^3)}{15m^2n^2} = 3m^4 + 2mn^3 + 4m^2n - 6m^2n^3$.
Ответ: $mn; 15mn; 15m^2n^2$.