What is the formula to find the missing term.
How to the common difference d is the difference between consecutive terms.
Chack the first term, the common difference, and the position of the missing term.
Class 10th Maths, CBSE Board and Others state Board 2022-2023.
In the following APs, find the missing terms in the boxes : _, 13, _, 3
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Here, a₂ = 13 and a₄ = 3. To find: a₁ and a₃
Given that: a₂ = a + (2 -1)d = 13
⇒ a + d = 13
⇒ a = 13 – d ….(1)
and a₄ = 3 ⇒ a + 3d = 3
Putting the value of a from equation (1), we get
13 – d + 3d = 3 ⇒ d = – 5
Putting the value of d in eqation (1), we get
a = 13 – (-5) = 18
Therefore, a₁ = 18 and a₃ = a + (3 – 1)d = 18 + 2(-5) = 8