Final answer:
The plus sign does not need to be written in ampersand notation in HTML, but other special characters like ÷, ≥, and √ should be encoded using HTML entity codes.
Step-by-step explanation:
In HTML, the plus sign (+) does not need to be written in ampersand notation because it is part of the standard HTML character set. The plus sign does not need to be written in ampersand notation in HTML, but other special characters like ÷, ≥, and √ should be encoded using HTML entity codes.
This means that you can use the plus sign directly in HTML without needing to encode it. However, the characters ÷, ≥, and √ are not part of the standard HTML character set, so to display them correctly, you should use their corresponding HTML entity codes, such as ÷ for ÷, ≥ for ≥, and √ for √.