Question

7) Na P.A. (-5,0-2,0+1, ...) determine o 10° termo e a soma dos 10 primeiros termos dessa P.A.

Answer 1

P. A. (-5,0; 2, 0;1,...)
a 10 = a 1 + ( n - 1 ).r
a 10 = -5,0 + (10 - 1).r
a 10 = -5,0 + 9 r
a 1 0 = -5,0 +9.-7
a 10 = - 5,0 - 63
a 10 = -68
S 10 = 10 (-5,0 -68 )/2
S 10 = 10 (-73 )/ 2
S 10 = -730 / 2
S 10 =- 365