Respuesta :

Answer: -4187

Step-by-step explanation:

-1,-4,-7

^ ^

+-3 +-3 -4- -1= -3

S53= 53/2 [2(-1)+(53-1)] -3

2(-1)= -2 (53-1) = 52•3 53/2=26.5

26.5 [ -2+ -156]= -4187