3)[(5x² - 4 cosx + 2)dx,

3) $$ \int (5x^2 - 4 \cos x + 2) dx = 5 \int x^2 dx - 4 \int \cos x dx + 2 \int dx = 5 \cdot \frac{x^3}{3} - 4 \sin x + 2x + C = \frac{5}{3}x^3 - 4 \sin x + 2x + C $$.

Ответ: $$\frac{5}{3}x^3 - 4 \sin x + 2x + C$$