My Math Forum How to find the length of an iron bar when it is given as a function of its size but

 Algebra Pre-Algebra and Basic Algebra Math Forum

March 5th, 2019, 01:41 PM   #21
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Joined: Jun 2017
From: Lima, Peru

Posts: 87
Thanks: 1

Math Focus: Calculus

Quote:
 Originally Posted by skipjack One can find values for m and n for any two consecutive values of x by substituting those values into 5x² + mx + n = 560, and then solving the resulting simultaneous equations for m and n. I asked for the Spanish so that I could make more Google searches for this problem or a similar one, but I found nothing relevant. Was your textbook written by a committee rather than by a mathematician?
Thanks. But I don't get very clearly where to substitue the values you mention. Can you show an example for one so I can deduce the others?. Perhaps, what you said is what I did in the attempt I posted earlier?. I'd like to know this to add it to my notes as this method you used I find it interesting.

Oh I see. Well, the book I'm using it was written by a committee and it is rather old. It included mathematicians but I believe there might be some errors or forced assumptions. Perhaps one problem or two suffer from this, but the majority seems to be okay. Actually the ones which had some degree of difficulty and I couldn't understand was the reason why I posted them here to look for help in the first place. I hope this has not caused you any problems.

March 5th, 2019, 01:48 PM   #22
Member

Joined: Jun 2017
From: Lima, Peru

Posts: 87
Thanks: 1

Math Focus: Calculus

Quote:
 Originally Posted by Denis Teachers in Peru appear to be as bad as teachers in America, inventing silly "stories" that only complicate the problem!! The problem could be simply and CLEARLY presented this way: The length of a steel bar is given by the function B(x)=5x^2+mx+n inches. The length of the steel bar is 560 inches. If the steel bar is cut in pieces of x inches in length, then a piece of length 20 inches is left; so x > 20. If the steel bar is cut in pieces of (x+1) inches in length, then a piece of length 10 inches is left. If the steel bar is cut in pieces of (x+2) inches in length, then what is the maximum number of pieces possible? Agree?
Hey. Don't blame me. I'm just doing my best effort to present the information which I have in the best way possible. I'm not aware of the current status of the education in America but to be honest probably what the person who "invented" this kind of story made it such a way to be a challenge in purpose for someone trying to solve it. Is that really neccessary?. I don't think so. But I agree with what you mentioned, it could had been stated as you mentioned and that's it.

Quote:
 Originally Posted by Denis Representative diagram (u,v,w = number of pieces): ---x---|---x---| ............................ |---x---|--20--| = 560 : ux + 20 = 560 ---x+1---|---x+1---| .................. |---x+1---|-10-| = 560 : v(x+1) + 10 = 560 ----x+2----|----x+2----| ............ |----x+2----|-y-| = 560 : w(x+2) + y = 560 Sorry: my diagram was NOT an attempt to solve. It's simply a representation (or picture) of the problem. Also, the "y" I show is apparently equal to 0: it was not clearly specified in the problem that 560 / (x+2) = an integer.
Oh I didn't know that it was just a representation. I would suggest you add more words of what you attempted to explain with that because I can't understand well what was the intended message. Anyways, any kind of help is always appreciated, at least by me. Even if there can be a subtle message of just pass. I've grown up to get through challenges. I am the kind of slow learner so be patience.

 Tags bar, find, function, iron, length, size

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