Question

calcule a soma dos termos da p.a., onde o primeiro termo é -2,r=4 e n=10

Answer 1

an=a1+(n-1)r
an=-2+(10-1)(4)
an=-2+36
an=34

Sn=(a1+an)n/2
Sn=(-2+34)10/2
Sn=(32)5
Sn=160

Answer 2

An=A1 + (n-1) . r
An = -2 +(10 -1) . 4
An= -2 + 36
An= 34

Sn= (A1 + An) . n/2
Sn= (-2 + 34) . 10/ 2
Sn= 32 . 10 / 2
Sn= 320/2
Sn= 160