Respuesta :

Answer:

The sum is equal to [tex]-905,200[/tex]

Step-by-step explanation:

we know that

The formula to calculate the sum is equal to

[tex]Sn=n\frac{(a1+an)}{2}[/tex]

In this problem

[tex]n=775[/tex] -----> number of terms

a1 is the first term

[tex]a1=(-3(1)-4)=-7[/tex]

an is the last term

[tex]an=(-3(775)-4)=-2,329[/tex]

substitute

[tex]Sn=775\frac{(-7-2,329)}{2}=-905,200[/tex]