Answer:
Answer: Sum of first 90 terms is Option d. 11655
Step-by-step explanation:
We have to find the sum of first 90 terms of the sequence -4,-1,2,5,8......
First we find the 90th term of the sequence
As we know the formula A(n)= A(1)+(n-1)d
Given from the sequence
A(1) = (-4)
n=90
d = 3
So A(n) = -4+(90-1)3
= (-4)+89×3
= 263
Now we know formula for the sum of any sequence is
Sum S(n) = [tex]\frac{n}{2}(A(1)+A(n))[/tex]
Now we know n= 90
A(1) = -4
A(n) =263
Now we put the value in the formula
S(n)= [tex]\frac{90}{2}(-4+263)[/tex]
= 45×259
= 11655
