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.
Step 1: Rewrite the expression
We can express the whole expression as follows:
\[
\left(\frac{1}{4}x^2 - 3x + 2.25\right) + \left(0.75x^2 + 2x - \frac{1}{4}\right)
\]
Step 2: Combine coefficients for like terms
For \(x^2\) terms:
\[
\frac{1}{4}x^2 + 0.75x^2
\]
We can convert \(0.75\) into a fraction:
\[
0.75 = \frac{3}{4}
\]
Now, add the \(x^2\) terms:
\[
\frac{1}{4}x^2 + \frac{3}{4}x^2 = \frac{1 + 3}{4}x^2 = \frac{4}{4}x^2 = 1x^2
\]
For \(x\) terms:
\[
-3x + 2x = -3x + 2x = -1x
\]
For constant terms:
Convert \(2.25\) into a fraction:
\[
2.25 = \frac{9}{4}
\]
Now combine the constants:
\[
\frac{9}{4} - \frac{1}{4} = \frac{9 - 1}{4} = \frac{8}{4} = 2
\]
Step 3: Write the result
Now combining all these results:
\[
1x^2 - 1x + 2 = x^2 - x + 2
\]
So the simplified expression is:
\[
\boxed{x^2 - x + 2}
\]