Question

A10 = 20; d = –1. Знайдіть a1.

Answer 1

a10 = 20

d = –1

аn = a1 + d(n-1)

20 = a1 -(10-1)

a1 -(10-1) = 20

a1 -9 = 20

a1 = 20 + 9

a1 = 29

Ответ: 29.

Answer 2

Ответ: а1=а10-9*d=20+9=29.

Объяснение:

Answer 3

To find the value of a1, we can use the formula for the nth term of an arithmetic sequence:

an = a1 + (n - 1)d

Given that A10 = 20 and d = -1, we can substitute these values into the formula:

A10 = a1 + (10 - 1)(-1)

20 = a1 + 9(-1)

20 = a1 - 9

To isolate a1, we add 9 to both sides of the equation:

a1 = 20 + 9

a1 = 29

Therefore, the value of a1 is 29.