Math, asked by arsh20320, 1 year ago

if the sum of P term of an ap is Q and the sum of Q terms is P show that sum of (p+q) terms is -(p+q)​

Answers

Answered by rdsharma07
2

REFER ATTACHMENT FOR YOUR SOLUTION DEAR..

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Answered by siddhivd16
8

Step-by-step explanation:

let \:  a \: be \: the \: first \: term \: and \: d \: be \: the \: common \: difference \: of \: the \: given \: a.p. \\ then \: sp \:  =  \: sq \:  \:  \:  \:  \:  \: ....(given) \\ using \: formula \:  \\ sn =  \frac{n}{2} (2a \:  + (n - 1)d)\:  \\  \frac{p}{2} (2a + (p - 1)d) =   \frac{q}{2} (2a + (q - 1)d) \\ p(2a + (p - 1)d) = q(2a + (q - 1)d) \:  \:  \:  \: .....(multiplying \: by \: 2) \:  \\ p(2a) + p(p - 1)d - q(2a) - q(q - 1)d = 0 \\ p(2a) - q(2a) + (p(p - 1) - q(q - 1)d = 0 \\ 2a(p - q) + ( {p}^{2}  - p -  {q}^{2}  + q)d = 0 \\ 2a(p - q) + ( {p}^{2}  -  {q}^{2}  - p + q)d = 0 \\ 2a(p - q) + ((p - q)(p + q) - (p - q)) = 0 \\ 2a(p - q) + (p - q)(p + q - 1)d = 0 \\ (p - q)(2a + (p + q - 1)d) = 0 \\ but \:  \\ p  \: is \: not \: equal \: to \: q \:  \: ...(given) \\ (p - q) \: is \: not \: equal \: to \: 0 \\ 2a + (p + q - 1)d = 0 \:  \: ....(1) \\ now \\ sp + q \:  =  \frac{p + q}{2} (2a + (p + q - 1)d) \\  =  \frac{p + q}{2}  \times 0 \:  \: ....(from \: 1) \\  = 0 \\ sp + q \:  = 0 \:  \\ the \: sum \: of \: first \: (p + q) \: terms \:  is \: 0.

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