Question

Uma PA Tem 18 termos ,sendo o primeiro termo é igual a 2 e a razão igual a 3

Answer 1

Resposta:

razão (r) = 3

termo 1 (t1) = 2

termo 2 (t2) = t1 + r = 2 + 3 = 5

termo 3 (t3) = t2 + r = 5 + 3 = 8

termo 4 (t4) = t3 + r = 8 + 3 = 11

termo 5 (t5) = t4 + r = 11 + 3 = 14

termo 6 (t6) = t5 + r = 14 + 3 = 17

termo 7 (t7) = t6 + r = 17 + 3 = 20

termo 8 (t8) = t7 + r = 20 + 3 = 23

termo 9 (t9) = t8 + r = 23 + 3 = 26

termo 10 (t10) = t9 + r = 26 + 3 = 29

termo 11 (t11) = t10 + r = 29 + 3 = 32

termo 12 (t12) = t11 + r = 32 + 3 = 35

termo 13 (t13) = t12 + r = 35 + 3 = 38

termo 14 (t14) = t13 + r = 38 + 3 = 41

termo 15 (t15) = t14 + r = 41 + 3 = 44

termo 16 (t16) = t15 + r = 44 + 3 = 47

termo 17 (t17) = t16 + r = 47 + 3 = 50

termo 18 (t18) = t17 + r = 50 + 3 = 53

Soma dos termos:

Sn = n * ( a1 + an ) / 2

S18 = 18 * (2 + 53) / 2

S18 = 18 * (55) / 2

S18 = 18 * 27,5

S18 = 495