Question

The algebraic form of an arithmetic sequence is 4n-5
(a) find its common difference
(b) find 10th term
(c) find the sum of the first 20th terms​.
please explain in step by step

Answer 1

Step-by-step explanation:

a1 = 4(1)-5 = 4 - 5 = -1

a2 = 4(2) - 5 = 8 - 5 = 3

d = a2 - a1 = 3 -(-1) = 4

a10 = a + (n-1)d

-1 +36 = 35

S20 = n/2 (2a + (n-1)d )

10(-2 + 76)

10(74) = 740

Answer 2

Answer.

a1 = 4(1)-5 = 4 - 5 = -1

a2 = 4(2) - 5 = 8 - 5 = 3

d = a2 - a1 = 3 -(-1) = 4

a10 = a + (n-1)d

-1 +36 = 35

S20 = n/2 (2a + (n-1)d )

10(-2 + 76)

10(74) = 740