Question

find the sum of 12 terms of an AP whose second and third terms are 9 and 13 respectively.​

Answer 1

Answer:

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Step-by-step explanation:

a

2

=14 and a

3

=18

Common difference, d=a

3

−a

2

=18−14=4

Now

a

2

=a+d=14

a+4=14

a=10

Now, sum of 51 terms

S

n

=

2

n

(2a+(n−1)d)

S

51

=

2

51

(2(10)+(51−1)4)

=

2

51

(20+200)

=

2

51×220

=51×110=5610

S

51

=5610

Answer 2

Step-by-step explanation:

i have attached the example

solve with the values