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Q5 of 89 Page 51

Determine the AP whose fifth term is 19 and the difference of the eighth term from the thirteenth term is 20.

Let the first term of an AP be a and common difference d.

Given

5^th term, a₅ = 19

And by using the nth term formula i.e. a_n = a + (n - 1)d

a + 4d = 19

a = 19 - 4d (eqn 1)

also,

20^th term - 8^th term = 20

a + 19d - (a + 7d) = 20

12d = 20

using this in eqn 1

So the AP is

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3

Write the first three terms of the AP’s, when a and d are as given below

4

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6

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Find the common difference and the number of terms.

7

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