Philippines Maths Olympiad 2020 Problem | PMO 2020 | Mathematics

Philippines Maths Olympiad 2020 Problem | PMO 2020 | Mathematics
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[@anthony17mapoy46]

Nice presentation of the given solution! I love it ❤...

[@MathBooster]

Thank you! 🙂

[@piman9280]

When finding the prime factors of 7601, why even consider if 9 is a factor (when 3 is not)?

[@abdoali6268]

Keep going 💪❤ from Egypt

[@Crazy_mathematics]

x = sin(θ) θ= cos(x) Find at what point x(θ)=θ(x)

[@vijayannair2316]

Nice

[@adgf1x]

20^5+21=2^5×10^5+21=3200021

[@birandkoray]

you have to prove that 3 digit numbers are prime

[@MathBooster]

It is given in the question that two prime factors of N are 3-digit numbers. So, if we get more that two 3-digit factors of N then only we need to check that which two numbers are prime. Otherwise there is no need to check.

[@timeonly1401]

For any 3-digit number n, it's easy enough to check all primes up to and less than the square root of the largest perfect square that's less than n. So, at worse, you'd try all the primes up to 31 (since the largest 3-digit perfect square is 31²=961): {2,3,5,7,11,13,17,19,23,29,31}. The largest perfect square just less than 421 is 20²=400, so try primes up to 19. For 691, the largest perfect square less than 691 is 26²=676, so try primes up to 23, which is only 9 primes; not that bad.

[@birandkoray]

@@timeonly1401 i expect this to be explained in the video