Question

S=17+18+19+.....+50 dau coroana

Answer 1

Răspuns:

Explicație pas cu pas:

S = 17 + 18 + 19 + ..... + 50

50 - 17 + 1 = 34 termeni are suma

S = 34 × ( 17 + 50 ) : 2

S = 34 × 67 : 2

S = 17 × 67

S = 1139

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Sau:

S = (1+2+3+ ....+ 16 + 17 + 18 + 19 + .... + 50 ) - ( 1+2+3+......+16)

S = 50 × ( 1 + 50 ) : 2 - [ 16 × ( 1 + 16 ) : 2 ]

S = 25 × 51 - 8 × 17

S = 17 × ( 25 ×3 - 8 )

S = 17 × 67

S = 1139