Question

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

Answer 1

Step-by-step explanation:

$\green\star$ Given

$\blue\star$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

Answer 2

Answer:

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