Let P be the set of 42nd roots of unity, and let Q be the set of 70th roots of unity. How many elements do P and Q have in common?
Let P be the set of 42nd roots of unity, and let Q be the set of 70th roots of unity. What is the smallest positive integer n for which all the elements in P and all the elements in Q are nth roots of unity?
I'll do number two for you, which should help you with number 1. If you are still confused, feel free to ask me.
2) Beneath all that ugly mathematician jargon lies a simple, beautiful, question: What is the LCM of 42 and 70? Solving this is simple, it gives us 210.
hint for number 1: If I told you should divide 210 into something, what would you do?
If you need more help, feel free to ask. Also, if my answer is wrong, please tell me, so I can correct it!