If you mean,
[tex] \frac{3}{4} - 4x + \frac{1}{2} x - \frac{1}{2} + \frac{1}{2}x[/tex]
Then the answer would be,
[tex] \frac{1}{4} - 3x[/tex]
But if you mean,
[tex] \frac{3}{4} - 4x + \frac{1}{2x} - \frac{1}{2} + \frac{1}{2x} [/tex]
Then the answer would be,
[tex] \frac{1}{4} - 4x + \frac{1}{x} [/tex]