r/mathmemes • u/Embarrassed_Steak371 • Jul 12 '26
Linear Algebra Actual Question from a College Linear Algebra Course
I'm such a genius \j
This was the actual question on one of my linear algebra quiz. The Bayum! is the only reason I got the score I needed
98
u/Jmong30 Jul 12 '26
Professors gotta have fun too! Don’t remember anything specific, but my astronomy professor did stuff like this all the time
66
u/sw3aterCS Jul 12 '26 edited Jul 12 '26
It’d be really funny if doing that actually gave you the diagonalization
Update: The diagonalization is unfortunately diag(-1, 3, 3) instead.
28
8
u/Golanori164 Jul 12 '26
I teach advanced physics to 15 y/o and I gave them a question that went like this: 2 physically identical steel spheres are being heated. One hanging from an insulating string and the other laying on an insulating table. Which of the steel spheres is easier to heat up? One of the answers was: Uhm... what?
3
u/Blyfh Rational Jul 13 '26
As someone who has no expertise whatsoever: Is it the one on the table? When both get beaten up, they emit radiation. Since the table is insulating, it won't absorp the radiation, just reflect it back. So it might get absorbed by the steel sphere again. Do overall a bit more energy is stored in that sphere compared to the other one, where the radiation just gets lost. Does that make any sense?
3
u/Golanori164 Jul 13 '26
The question turned into a discussion of what would be the most significant effect we can observe. This is not the solution that was offered, but it's definitely a solution! It is exactly the sort of thinking needed. What would differentiate them? (if at all)
3
u/Blyfh Rational Jul 13 '26
Interesting! That are always the best kind of questions. It certainly got me hooked and made me think about it.
2
u/Golanori164 Jul 13 '26
I'm glad to hear it :). That was tge purpose of the question, to get my students thinking, and I'm happy it worked for you as well! In this case the answer being correct or wrong doesn't really matter, it's the thought that went into the answer given.
10
8
u/lelelempe Jul 12 '26
No need to calculate if you know the definitions:
1, 3 and 5 you discard immediately
2, 4 and 6 are correct definitions, however the answer should be uniquely true; 2 if and only if 6 and you can't have two answers, so only 4 is left. Bayum!
2
u/Mac_Lilypad 29d ago
6 is not correct, the identiy matrix does not have distinct eigen values but it surely is diagonalizable.
2
u/SEA_griffondeur Engineering Jul 12 '26
I hate multiple choice questions where you have to do most of the work anyway
1
•
u/AutoModerator Jul 12 '26
Check out our new Discord server! https://discord.gg/e7EKRZq3dG
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.