Question

Calcule a soma dos trinta primeiros termos da pa 2 9 16 ?

Answer 1

Resposta:

Sn=(a1+an).n/2

an=a1+(n-1).r

a30=2+(30-1).7

a30=2+(29).7

a30=2+203

a30=205

Sn=(2+205).30/2

Sn=207.30/2

Sn=6210/2

Sn=3105

Answer 2

(2,9,16...)

r=9–2=7

a₃₀=a₃+27r

a₃₀=16+27.7

a₃₀=16+189

a₃₀=205

S₃₀=30.(a₁+a₃₀)/2

S₃₀=30.(2+205)/2

S₃₀=15.207

S₃₀=3105