Combine any like terms in the expression. If there are no like terms, rewrite the expression.

To combine the like terms in the expression \(10r^2 + 2r^2 - 4r^2\), you add and subtract the coefficients of \(r^2\):

\[ 10 + 2 - 4 = 8 \]

So, the combined expression is:

\[ 8r^2 \]

Thus, the final result is \(8r^2\).