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Question
In the following APs find the missing term in the box:
`square, 13, square, 3`
Solution
18, 13, 8, 3
Explanation:
For this A.P.,
a2 = 13 and
a4 = 3
We know that, an = a + (n − 1) d
a2 = a + (2 − 1) d
13 = a + d ...(I)
a4 = a + (4 − 1) d
3 = a + 3d ...(II)
On subtracting (I) from (II), we obtain
−10 = 2d
d = −5
From equation (I), we obtain
13 = a + (−5)
a = 18
a3 = 18 + (3 − 1) (−5)
= 18 + 2 (−5)
= 18 − 10
a3 = 8
Therefore, the missing terms are 18 and 8 respectively.
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