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समांतर श्रेणी

Question
CBSEHHIMAH10010198

नीचे दिए हुए योगफलों को ज्ञात कीजिए:
34 + 32 + 30 + . . . + 10

Solution

a = 34, d = – 2, an = 10 = l
an = a + (n – 1)
⇒ 10 = 34 + (n – 1) (–2)
⇒ 10 = 34 –2n + 2
⇒ 10 = 36 – 2n
⇒ –26 = –2n ⇒ n = 13
straight S subscript straight n space equals space straight n over 2 space left square bracket space straight a space plus space 1 space right square bracket
straight S subscript 13 space equals space 13 over 2 space left square bracket space 34 plus space 10 space right square bracket space equals space 13 over 2 space cross times space 44
equals space 13 space straight x space 22 space equals space 286