Is (x + a + b)^7 - x^7 - a^7 - b^7 Divisible by x^2 + (a + b)x + ab?

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Discussion Overview

The discussion revolves around the mathematical problem of determining whether the expression (x + a + b)^7 - x^7 - a^7 - b^7 is divisible by the polynomial x^2 + (a + b)x + ab. The scope includes mathematical reasoning and problem-solving approaches related to polynomial divisibility.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in solving the problem, suggesting it seems more complex than it is.
  • Another participant implies that the problem can be solved completely, hinting at a dismissive attitude towards seeking an easy solution.
  • A third participant reiterates the original problem and provides a hint that the factors (x + a) and (x + b) are relevant, suggesting that proving divisibility by these factors would suffice.
  • Another participant suggests expanding the expression and rewriting terms to demonstrate divisibility, although they do not provide specific steps.
  • A participant comments on the daunting nature of expanding a trinomial to the seventh power, indicating a shared concern about the complexity of the task.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the approach to solving the problem, with some suggesting different methods and expressing varying levels of confidence in the task's difficulty.

Contextual Notes

Some assumptions about the properties of polynomials and divisibility are present, but they are not explicitly stated or agreed upon by all participants. The discussion lacks detailed mathematical steps that would clarify the reasoning behind the proposed approaches.

Who May Find This Useful

This discussion may be useful for students or individuals interested in polynomial algebra, particularly those grappling with problems involving divisibility and expansion of expressions.

Hyperreality
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My maths teacher says this problem is not as impossible as it seems, but I just can't solve it.

Show that (x + a + b)^7 - x^7 - a^7 - b^7 is divisble by
x^2 + (a + b)x +ab.
 
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Looking for the easy way out huh ?
You can always solve the entire exercise...

Live long and prosper.
 
Show that (x + a + b)^7 - x^7 - a^7 - b^7 is divisble by x^2 + (a + b)x +ab.

Hint:
Notice that (x+a) and (x+b) are the 2 factors of x^2 + (a + b)x +ab.
So it is equivalent to show that (x + a + b)^7 - x^7 - a^7 - b^7 is divisible by both (x+a) and (x+b).

Let f(x) = (x + a + b)^7 - x^7 - a^7 - b^7
...
...
...
...


Can you continue from here?

Hope this help. :smile:
 
just write everything out
eg. (x+a)^2=x^2+2xa+a^2

maybe rewrite some terms then and you will see that it is divisible by x^2 + (a + b)x +ab
 
KL has the easy way!

Writing it out however... *shudder* I wouldn't wish writing out a trinomial to the 7th power to anyone!

Hurkyl
 

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