Array Formulas in Excel

The brackets { } around a formula indicate that it is an array formula. An array formula is a special type of formula that can perform calculations on multiple values in one or more arrays, and return a single result or multiple results.

When you copy an array formula to extend the data range, the brackets { } should automatically adjust to include the new range. However, if the brackets disappear and the formula stops working, it could be due to a few reasons:

1. You may have accidentally deleted the brackets while copying the formula. In this case, you can try copying the formula again and make sure to include the brackets.
2. The new range may not be the same size or shape as the original range. Array formulas require that all arrays have the same number of rows and columns. If the new range is not the same size or shape, the formula may not work correctly. To fix this, you can adjust the range to match the original range.
3. The formula may not be entered as an array formula. To enter a formula as an array formula, you need to press Ctrl + Shift + Enter instead of just Enter. This tells Excel that you are entering an array formula and it will automatically add the brackets { } around the formula.

In summary, the brackets { } around a formula indicate that it is an array formula. If the brackets disappear when you copy the formula, it could be due to accidentally deleting them, the new range not being the same size or shape as the original range, or not entering the formula as an array formula.