Question

Va rog urgent!!! S1 = 5+8+11+14+...+92 S2 = 1+6+11+16+...+101

Answer 1

Răspuns:

Explicație pas cu pas:

S₁ = 5+8+11+14+.....+92

→ progresie aritmetică cu rația 3 ( 8-5=3; 11-8=3....)

(92 - 5) : 3 + 1 = 87 : 3 + 1 = 29+1 = 30 termeni are suma

S₁ = 30×( 5+92) : 2

S₁ = 15 × 97

S₁ = 1455

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S₂ = 1+6+11+16+......+101

(101 - 1) : 5 + 1 = 100 : 5 + 1 = 21 termeni are suma

S₂ = 21 × ( 1+101) : 2

S₂ = 21 × 102 : 2

S₂ = 21 × 51

S₂ = 1071