Coefficients of trinomial theorem

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The discussion centers on the trinomial theorem and its relationship to Pascal's tetrahedron, particularly in expanding the expression (x+y+z)^5. It highlights the coefficients derived from the trinomial expansion, which differ from the simpler binomial coefficients used in linear developments. The coefficients for the trinomial expansion involve a combination of binomial numbers, indicating a more complex selection process. Participants express curiosity about how to calculate these coefficients, referencing the multinomial theorem for further clarification. Understanding these coefficients is essential for accurate trinomial expansions in algebra.
Jhenrique
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There is a trinomial theorem relationed with the Pascal's tetrahedron, so that...

(x+y+z)^5=
<br /> \\ +01x^5y^0z^0+05x^4y^1z^0+10x^3y^2z^0+10x^2y^3z^0+05x^1y^4z^0+01x^0y^5z^0<br /> \\ +05x^4y^0z^1+20x^3y^1z^1+30x^2y^2z^1+20x^1y^3z^1+05x^0y^4z^1<br /> \\ +10x^3y^0z^2+30x^2y^1z^2+30x^1y^2z^2+10x^0y^3z^2<br /> \\ +10x^2y^0z^3+20x^1y^1z^3+10x^0y^2z^3<br /> \\ +05x^1y^0z^4+05x^0y^1z^4<br /> \\ +01x^0y^0z^5<br />

Well, when it comes the binomial coefficients, they are easily determined so:

\binom{5}{0}...\binom{5}{1}...\binom{5}{2}...\binom{5}{3}...\binom{5}{4}...\binom{5}{5}
But this sequence is for a linear development (binomial theorem). And when it comes to a bilinear development (trinomial theorem), how will be the coefficients? Certainly, there will a product between binomial numbers, but how will be such scheme?
 
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Hi Jhenrique! :wink:

The coefficient of xaybzc wil be the number of ways of choosing a of this b of that and c of the other out of a+b+c,

which is … ? :smile:
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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