Add. \( \left(5 c^{2}+8 f^{2}+4\right)+\left(4 c^{2}-6 f^{2}-2\right) \) \( \left(5 c^{2}+8 f^{2}+4\right)+\left(4 c^{2}-6 f^{2}-2\right)=\square \)

To combine the expressions, we can group the like terms together. Starting with the expression: \[ (5 c^{2} + 8 f^{2} + 4) + (4 c^{2} - 6 f^{2} - 2) \] We can add the coefficients of \( c^{2} \): \[ 5 c^{2} + 4 c^{2} = 9 c^{2} \] Next, we add the coefficients of \( f^{2} \): \[ 8 f^{2} - 6 f^{2} = 2 f^{2} \] Now, we add the constant terms: \[ 4 - 2 = 2 \] Putting it all together, we have: \[ 9 c^{2} + 2 f^{2} + 2 \] So, the final answer is: \[ \left(5 c^{2}+8 f^{2}+4\right)+\left(4 c^{2}-6 f^{2}-2\right) = 9 c^{2} + 2 f^{2} + 2 \]