... a^2 - 8a + 16 - 6a^2 + 8a = 16 - 5a^2.
3^cosx / 9^cos^2x = 3^cosx / 3^2cos^2x = 3^(cosx - 2cos^2x);
3^(cosx - 2cos^2x<span>) = 4^(2cos^2x - cosx);
</span>3^(cosx - 2cos^2x) * 4^(cosx - 2cos^2x) = 1;
12^(cosx - 2cos^2x) = 1;
cosx - 2cos^2x = 0;
cosx * (1 - 2cosx) = 0;
cosx = 0; x = Pi/2 + Pi*n; n ∈ Z;
1 - 2cosx = 0; cosx = 1/2; x = +-Pi/3 + 2Pi*n; <span>n ∈ Z;
Ответ: x = </span>Pi/2 + Pi*n, +-Pi/3 + 2Pi*n; <span>n ∈ Z.</span>
2d ^18+2x^18-2d^18+2x^18-d^2 x^2=4x^18-d^2x^2=x^2(4x^16-d^2) =x^2(2x^8-d)(2x^8+d)