Respuesta :

Answer:

17900

Step-by-step explanation:

First term a = -19

common difference d = -15-(-19) = 4

number of terms, n = 100

sum of first 100 terms,

n/2(2a+(n-1)d)

= 100/2(2×(-19)+(100-1)4)

= 50×(-38+99×4)

= 50×358

= 17900