1997 AIME Problems/Problem 1
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Problem
How many of the integers between 1 and 1000, inclusive, can be expressed as the difference of the squares of two nonnegative integers?
Solution
If we let the two squares be 
, then by difference of squares we have 
. Notice that 
and 
have the same parities. This eliminates all numbers in the form of 
: when 
is factored, one of the factors must be even, but not both, so its factors cannot have the same parity.
The remaining 
numbers, we can describe specific squares which fit the conditions:
- For all odd
, 
.
- For all
, 
.
See also
| 1997 AIME (Problems • Resources) | ||
| Preceded by First Question | Followed by Problem 2 | |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 | ||
