What is the sum of the arithmetic series: s10 = -20, d = 4, a1 =?

first term a1 is -40.

Step-by-step explanation:

in an arithmetic series,

sum of first term terms (S10) = -20

Common difference (d) = 4

first term (a)= ?

number of terms (n)= 10

now,

S10 =( n÷2) [a1 +(n-1) d]

or, -20 = (10÷2) [a1 + (10-1) 4]

or, -20 = 5 ( a1 + 36)

or, -4 = a1 + 36

or, a1 = -40

a. 19,958,400

step-by-step explanation:

hope this