What are the first term and the common difference of an A.P. if the third term is 8 and seventh term is 20 ?

Expert Answers

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The question is basically asking:

Term no: 1, 2, 3, 4, 5, 6, 7, ...

Nos:        ?, _, 8, _, _, _, 20, ...

By inspection,

Common diff

=(20-8)/(7-3)

= 12 / 4

= 3

 

1st term

= 8 - 2x3

= 8 - 6

= 2

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