Here is a list of math expressions that equal the numbers from 1 to 100 using only the numbers 1, 4, 5, and 9. Each number must be used exactly once, and you can use any combination of operations. I'll start with a few examples and continue working through the list:

1. $(9 + 5 - 4 - 1) = 9$
2. $(5 - 4) \times (9 - 1) = 8$
3. ( (9 \times 1) + (5 - 4) = 10