Final answer:
The closest approximation to the value of √13 + √21 is 8.
Step-by-step explanation:
To find the closest approximation to the value of √13 + √21, we need to calculate the square roots and add them together. Using a calculator, we find that √13 ≈ 3.6056 and √21 ≈ 4.5826. Adding these values together, we get approximately 8.1882. The closest whole number to this value is 8.
Therefore, the closest approximation to the value of √13 + √21 is 8.