Скачать или смотреть Discover the QUICK and EASY Way to Check if a Large Number is PRIME | 8 Sec Trick

Struggling to find out whether a big number is prime or composite?🤔
In this video, I’ll teach you quick and easy tricks to check if a large number is prime — without doing endless divisions!
✅ Learn powerful math hacks like:
• Divisibility rules for small primes
• The Square Root Test for faster checking
• The 6n ± 1 rule to identify prime candidates

💡 These tricks are perfect for students, teachers, and competitive exam aspirants who want to master prime numbers quickly.

TimeStamps
00:00 – Introduction
00:50 – Prime vs Composite Basics
01:56 – Quick Divisibility Rules for 2, 3, 5, 7, 11
04:30 – The Square Root Rule Explained
07:00 – The 6n ± 1 Trick

Introduction:
o Prime number → only 2 factors: 1 and itself.
o Composite number → more than 2 factors

Method 1 – Quick Divisibility Rules
Simple rules for small primes:
• Divisible by 2 → even number.
• Divisible by 3 → sum of digits multiple of 3.
• Divisible by 5 → ends with 0 or 5.
• Divisible by 11 → difference of alternating digits divisible by 11.

Method 2 – Square Root Rule
To test primality, you only need to check divisibility up to √N.
• Example: 7919
o √7919 ≈ 89.
o So, check primes ≤ 89 only (2, 3, 5, 7, 11, 13, … 89).
o None divide → 7919 is prime.

Method 3: The quick and Easy 8 Sec Trick of 6n ± 1 for Testing Primes
Numbers of the form 6n-1 and 6n+1 are candidates for primes, as all prime numbers greater than 3 must be of this form. However, not all numbers in the 6n±1 form are prime, as seen with examples like 25 (64+1) and 35 (66-1). To use this for primality testing, you first check if the number is 2 or 3; if not, check if it fits 6n±1, and if it does, you must then perform a full trial division to confirm it has only two factors.
So, If it fits 6n±1: This indicates the number might be prime, but it's not guaranteed.
This rule is necessary but not sufficient.
• If a number is prime, it must be in the form 6n±16n ± 16n±1.
• But not all numbers of the form 6n ± 1 are prime (e.g., 25 = 6×4 + 1, but it’s composite).

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