Question

Answer the following questions:

There are 21 terms in an Arithmetic progression. The sum of last three terms
is 123 and the sum of the three middle terms is 69. Find the Arithmetic
progression.

ans plz​

Answer 1

Step-by-step explanation:

we have

n=21

the sum of first three terms is 123

a+a2+a3=123

a+a+2d+a+3d=123

3a+5d=123 _________(1)

the sum of three middle terms are 69

a10+a11+a12=69

a+9d+a+10d+a+11d=69

3a+30d=69 ________(2)

subtracting (1) and (2)

3a+5d-3a-30d=123-69

-25d=54

d=-54/25

d=-2.16

3a+30d=69

dividing by 3 on both sides

a+10d= 23

a+21.6=23

a= 23-21.6

a=-1.39

thus the ap is

-1.39;-3.55....

Answer 2

hope it helps u

Step-by-step explanation:

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