Answer
$\frac{-3}{4}a^{2}+2b^{2}$
Work Step by Step
We begin by combining like terms. To combine like terms, simply add the coefficients of like variables together. In this case $-a^{2}$ and $.25a^{2}$ are like terms.
$-a^{2}+2b^{2}+.25a^{2}$ = $\frac{-3}{4}a^{2}+2b^{2}$