Online Course Discussion Forum

2.26, 2.28 primes and factors

 
 
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2.26, 2.28 primes and factors
by effie wei - Wednesday, 13 March 2024, 9:46 AM
 
Hi I need help on how to do the problems 2.26 and 2.28 on the lesson Primes and Factors.I don't have an idea on how to do the problem and what I need to do.
 
Picture of John Lensmire
Re: 2.26, 2.28 primes and factors
by John Lensmire - Thursday, 14 March 2024, 11:56 AM
 

This is for MC I-A, right?

Note 2.26 (and similarly 2.27) are really just two questions asked together. For 2.26 the problem wants you to find the prime factorization of 325 and then separately find the prime factorization of 391. Recall, for example, the prime factorization of 180 is 2^2 * 3^2 * 5.

For 2.28, here's a hint: Consider the number 9876543. The sums of the pairs of consecutive numbers are 9+8=17 (prime), 8+7=15 (not prime), 7+6=13 (prime), etc., until 4+3=7 (prime). The problem is asking to find the smallest number so that ALL of these sums are prime.

Hope this helps!

Note we're also having a live office hour later today (Thursday 3/14) from 5:30-6:30pm Pacific on our Discord at https://discord.gg/fUVvJUW9?event=1217524237607374868 Even if you can't make the live office hours, the Discord can be a good place to ask questions in addition to this forum.