2. \( 5 c^{2}+7 d \)

Did you know that polynomial expressions like \( 5c^2 + 7d \) are the building blocks of algebra? They can represent a wide range of real-world scenarios, from calculating areas in geometry to modeling physical systems in physics! Each term (like \( 5c^2 \) or \( 7d \)) encapsulates key variables and coefficients that contribute to the overall function. When dealing with polynomial expressions, a common mistake is to confuse terms during simplification or while combining like terms. Remember, you can only add or subtract coefficients of the same base and exponent. So in this case, \( 5c^2 \) and \( 7d \) are unique and can't be combined further, but it's important to keep track of your variables!