6 ms·
A trick for remembering that 91 is composite is that it's of the form x² - y² (specifically 10² - 3²), so it's (x+y)(x-y) or 13 * 7.
by _kst_ 5y ago
A trick for remembering that 91 is composite is that it's of the form x² - y² (specifically 10² - 3²), so it's (x+y)(x-y) or 13 * 7.
- canjobear 5y agoseems easier to remember "91 is composite"
- deleted 5y ago[deleted]