2 Answers

Tom Winter · Answer 1 · 2021-05-07T21:42:29+0000

Answer:

first term a1 is -40.

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

Adam Rackis · Answer 2 · 2021-05-11T16:21:13+0000

Explanation:

$\blue\star$ s10 = -20

$\blue\star$ n = 10

$\blue\star$ an = -20

$\green\star$ solution

$\green\star$ s10 = n\2 [a+(n-1)d]

$\green\star$ -20 = 10a2[a+(10-1)4]

$\green\star$ -4 = a +36

$\green\star$ a1 = -40

$\small\boxed{a = -40}$

Hope it helps.

Hope it helps