Question

{a2+a6+a9=45 {a3+a7+a10=54​

Answer 1

Răspuns:

a₁ = 1 ; r = 3

Explicație pas cu pas:

{a₂+a₆+a₉ = 45

{a₃+a₇+a₁₀ = 54

a₂ = a₁+r ; a₆ = a₁+5r ; a₉ = a₁+8r

a₃ = a₁+2r ; a₇ = a₁+6r ; a₁₀ = a₁+9r

{a₁+r+a₁+5r+a₁+8r = 45

{a₁+2r+a₁+6r+a₁+9r = 54

3a₁+14r = 45

3a₁+17r = 54  => 3r = 54-45 => r = 3

a₁ = (45-14·3)/3 => a₁ = 1

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