How Did 1886 Dutch Students Solve This Complex Math Problem?

Click For Summary
The discussion revolves around solving a complex math problem from an 1886 Dutch high school exam, specifically the equation involving cube roots. Participants express admiration for the students who solved it and share various approaches to reach the book's solutions, which are x = (7/9)a and x = (13/14)a, with a ≥ 0. Some contributors suggest techniques like substituting variables and manipulating the equation into a quadratic form, while others discuss the challenges of high school math education today compared to the past. The conversation highlights differing perspectives on problem-solving methods and the perceived decline in mathematical proficiency among current students.
  • #31
Frabjous said:
So what? You get one value of x for one value of a. The OP has the solution which has TWO values of x for a given value of a. The OP also has the solution for other values of a. You are missing a lot of solutions.
I will check if I can get other values by changing my ##m## value. Cheers man!
 
Physics news on Phys.org
  • #32
You are going to come up with a finite number number ‘n‘ of solutions. Given that there are an infinite number of solutions, your grade for the problem will be n/∞=0. :wink:
 
  • #33
@chwala ,
Your response to my post (#22), although I made a mistake in that post of mine. It is corrected here:
SammyS said:
(My post (#22) in reference to your post (#19) )
It looks like you intended to divide both sides buy ##(a+x)^\frac{1}{3}## but you neglected dividing ##5(a-x)^\frac{1}{3}## by ##(a+x)^\frac{1}{3}## .

Correction:
... you neglected to divide ##6(a-x)^\frac{2}{3}## by ##(a+x)^\frac{1}{3}## .

Your post(#23)
chwala said:
This may be unorthodox approach but hey let us do it!

We have,

##(a+x)^{\frac{2}{3}} + 6 (a-x)^{\frac{2}{3}}=5(a^2-x^2)^{\frac{1}{3}}##

I will still let

##m=a+x##

and

##k=a-x##

then,

##m^{\frac{2}{3}} + 6k^{\frac{2}{3}}=5m^{\frac{1}{3}}k^{\frac{1}{3}}##
(I'll cut in here.)

This looks fine. In fact you could write that as;

##\displaystyle m^{\frac{2}{3}} -5m^{\frac{1}{3}}k^{\frac{1}{3}}+ 6k^{\frac{2}{3}}=0## ,

which can be factored quite nicely, by the way.

You then go on to state;
##6k^{\frac{2}{3}}=m^{\frac{1}{3}}[5k^{\frac{1}{3}}-m^{\frac{1}{3}}]##

Let

##m^{\frac{1}{3}}=1##

then,

##6k^{\frac{2}{3}}-5k^{\frac{1}{3}}+1=0##
...

the other steps to solution shall remain as shown on the quoted post.

cheers!
Although you get the same quadratic equation as you did in the "quoted post" (#19), that is only due to the choice of ##m=1##.

For other values of ##m##, posts 19 and 22 will not agree.
 
  • #34
SammyS said:
@chwala ,
Your response to my post (#22), although I made a mistake in that post of mine. It is corrected here:Your post(#23)
(I'll cut in here.)

This looks fine. In fact you could write that as;

##\displaystyle m^{\frac{2}{3}} -5m^{\frac{1}{3}}k^{\frac{1}{3}}+ 6k^{\frac{2}{3}}=0## ,

which can be factored quite nicely, by the way.

You then go on to state;

Although you get the same quadratic equation as you did in the "quoted post" (#19), that is only due to the choice of ##m=1##.

For other values of ##m##, posts 19 and 22 will not agree.
Thanks can see that we end up with what was previously found by other members:

... i.e

##x^2-5xy+6y^2=0##

##(x-2y)(x-3y)=0##

...

where;

##x=m^\frac{1}{3}##

and

##y=k^\frac{1}{3}##
 
  • #35
Mark44 said:
Based on @vanhees71's subsequent response, he evidently meant "integration by parts." It's possible that he conflated the names of the techniques of integration by parts and integration by partial fraction decomposition.
I think it's a "Germanism", because in German we call this technique "partielle Integration". Obviously in English it's exclusively called "integration by parts".
 
  • Informative
Likes hutchphd and chwala

Similar threads

  • · Replies 10 ·
Replies
10
Views
2K
Replies
2
Views
3K
Replies
7
Views
2K
  • · Replies 10 ·
Replies
10
Views
475
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
4
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 61 ·
3
Replies
61
Views
11K