Recent content by James_fl

arunbg: My teacher said that it is wrong but she did not tell what is her answer. So i sent her an e-mail asking what is the correct answer, but she hasn't got back to me. And unfortunately, e-mail is the only available form of communication since this course is an online course. Can I ask...

arunbg: that's what i thought also, but my teacher said that it's wrong.. Any idea why?

Hi, could someone please verify my answer? Thanks.. :smile: How many 4-letter words can be made from the letters of the word PULLEYS? Explain your answer. There are two mutually exclusive cases by which four letter-word can be arranged from the word PULLEYS. Let n(A) be the number of...

TD: Cool, that clears up a lot of issues! Thank you all for the help, now I am going to write this answer down!

Yes, thank you matt grime :wink:

TD: ok I got it :smile: Thank you.

whoa a lot of replies.. so the n! function is injective for all values of n except 0 and 1, right?

matt grime: No need to be hostile, I am just a high school student looking to understand a concept. Maybe "argument" is not the correct word since it is only my assumption. I understand to prove a statement, I need to prove it for a general case. So in that sense, 5! = x! means x=5 does not...

I think I need to clarify. I don't know if it is injective or not, but if it is not injective, and I'm sorry to repeat this, why if 5! = x! then x=5? While it TD is right in saying that it wouldn't work for some numbers, I still don't get it. Possibly, there is some circular logic in my...

TD: Yes, it doesn't work for 1!, but why? I'm confused :(

dav2008: yes, i could, which means the factorial function is also not injective. But how could a function be injective (assuming my argument is true) and not injective at the same time?

matt grime: if factorial function is not injective, then why is it that i can show by inspection: if 5! = x!, then x=5? My Math knowledge is limit, so my apology if I am mistaken, but surely, there is no other value that can satisfy x except 5?

No, because the 5 in f(x) = 5 is a constant. Does this have something to do with the fact that the value 0!=1 and 1!=1 are defined; and hence they are constants? If so, how should I put it down to words?

Well obviously, no is the answer. But why? After all: If 5! = x! then x = 5.

[REVISED]My apology for forgetting to post the question.. Hello, I have a problem to solve this question. I am sure that I have done a mistake somewhere since it is impossible to solve: 246.25 sin x - 676.58 cos x = -27768.42 (last line) Question: Use Cartesian vector method to solve all the...