\[1)\ y^{'} = 3 - 4x;\]
\[y = 3x - 4 \bullet \frac{x^{2}}{2} + C =\]
\[= 3x - 2x^{2} + C.\]
\[2)\ y^{'} = 6x^{2} - 8x + 1;\]
\[y = 6 \bullet \frac{x^{3}}{3} - 8 \bullet \frac{x^{2}}{2} + x + C =\]
\[= 2x^{3} - 4x^{2} + x + C.\]
\[3)\ y^{'} = 3e^{2x};\]
\[y^{'} = 3 \bullet \frac{1}{2}e^{2x} + C = \frac{3e^{2x}}{2} + C.\]
\[4)\ y^{'} = 4\cos{2x};\]
\[y = 4 \bullet \frac{1}{2}\sin{2x} + C =\]
\[= 2\sin{2x} + C.\]