Simplify (1/4x^2 - 3x + 2.25) + (0.75x^2 +2x - 1/4)

To simplify the expression \((\frac{1}{4}x^2 - 3x + 2.25) + (0.75x^2 + 2x - \frac{1}{4})\), we will first combine like terms.

1. Identify the coefficients for each type of term (quadratic, linear, and constant):

- For \(x^2\) terms:
\[
\frac{1}{4}x^2 + 0.75x^2
\]

- For \(x\) terms:
\[
-3x + 2x
\]

- For constant terms:
\[
2.25 - \frac{1}{4}
\]

2. Combine the \(x^2\) terms:
\[
\frac{1}{4} + 0.75 = \frac{1}{4} + \frac{3}{4} = 1 \quad \text{(since \(0.75 = \frac{3}{4}\))}
\]

3. Combine the \(x\) terms:
\[
-3 + 2 = -1
\]

4. Combine the constant terms:
\[
2.25 - \frac{1}{4} = 2.25 - 0.25 = 2
\quad \text{(since } \frac{1}{4} = 0.25\text{)}
\]

5. Now combine all these results:
\[
1x^2 - 1x + 2
\]

So, the simplified sum of the polynomials is:
\[
x^2 - x + 2
\]

Thus, the final answer is:
\[
\boxed{x^2 - x + 2}
\]