The sum of (p + q)th and (p – q)th terms of an AP is equal to

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NDA (Held On: 21 Apr 2019) Maths Previous Year paper
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  1. (2p)th term
  2. (2q)th term
  3. Twice the pth term
  4. Twice the qth term

Answer (Detailed Solution Below)

Option 3 : Twice the pth term
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Concept:

The nth term of an AP is given by: Tn = a + (n - 1) × d, where a = first term and d = common difference.

Calculation:

As we know that, the nth term of an AP is given by: Tn = a + (n - 1) × d, where a = first term and d = common difference.

Let a be the first term and d is the common difference.

\(\Rightarrow \;{a_{p + q}} = a + \left( {p + q - 1} \right) \times d\)     ...1)

\(\Rightarrow \;{a_{p - q}} = a + \left( {p - q - 1} \right) \times d\)     ...2)

By adding (1) and (2), we get

\(\Rightarrow \;{a_{p + q}} + {a_{p - q}} = 2\;a + 2\;\left( {p - 1} \right)d = 2 \times \left[ {a + \left( {p - 1} \right)d} \right] = 2 \times {a_p}\)
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