Final answer:
To simplify the given algebraic expression (D^2+6D+9)+(D^3-6D+9), we combine like terms to arrive at the final simplified form D^3+D^2+18.
Step-by-step explanation:
The question provided involves algebraic polynomial addition. To solve the expression (D2+6D+9)+(D3-6D+9), we must combine like terms. This involves adding coefficients for terms that have the same variables raised to the same power.
To simplify the given expression, first, write out all terms:
D3 + D2 - 6D + 6D + 9 + 9.
Then, combine like terms:
D3 + D2 + 0D + 18.
The final simplified expression is D3 + D2 + 18.