Question

find the sum if the first 20 terms of the arithmetic sequence 8,14,20........​

Answer 1

Answer:

Hi!!!

a = 8

d = (14-8) = 6

n=20

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

S = 20/2(8 + (20-1)6)

S = 10(8 + (19)6)

S = 10(8 + 114)

S = 10(122)

S = 1220.

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Answer 2

Step-by-step explanation:

Arithmetic sequence = 8, 14, 20......

= 8, (8+6), (8+2*6).......

its in Ap form a, (a+d), (a + 2d )

d = a2- a1 = 14- 8 = 6

d= 6

a= 8

*** Sn = n/2 [2a +( n-1)d]

S20 = 20/2 [ 2*8 +(20-1)6]

S20 = 10 [ 16 + (19) 6]

S20 = 10 [ 16 + 114 ]

S20 = 10 [130]

S20 = 1,300

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