Math Problem Statement
◦ Somme triangulaire.
Si αi,j sont des réels indicés par i ∈ J1, nK et j ∈ J1, nK, alors :
Pn
i=1
Pn
j=i αi,j =
Pn
j=1
Pj
i=1 αi,j
Exemple.
Pn
i=1
Pn
j=i i/j =
Pn
j=1
Pj
i=1 i/j =
Pn
j=1(1/j) ×
Pj
i=1 i =
Pn
j=1(1/j) × j × (1 + j)/2 =
Pn
j=1(1 + j)/2 =
(1/2) ×
Pn
j=1(1 + j) = (1/2) ×
Pn+1
j=2 j = n × (n + 3)/4.
Solution
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Math Problem Analysis
Mathematical Concepts
Triangular Sums
Double Summation
Algebra
Formulas
∑_{i=1}^{n} ∑_{j=i}^{n} α_{i,j} = ∑_{j=1}^{n} ∑_{i=1}^{j} α_{i,j}
∑_{i=1}^{n} ∑_{j=i}^{n} i/j = ∑_{j=1}^{n} ∑_{i=1}^{j} i/j = n(n+3)/4
Theorems
Properties of Summation
Symmetry of Summation Indices
Suitable Grade Level
University Level (Mathematics, Algebra)
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