यदि C(20, n + 2) = C(20, n – 2) है तो n किसके बराबर है?

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NDA (Held On: 21 Apr 2019) Maths Previous Year paper
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Answer (Detailed Solution Below)

Option 2 : 10
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धारणा:

संकेतन C (n, r) एक बार में r चीजें लेने वाली n विभिन्न चीजों के संयोजन/समूहों की संख्या है और इसे निम्न द्वारा दिया गया है:

यदि C(n, x) = C(n, y), तो x + y = n।

गणना:

दिया हुआ C(20, n + 2) = C(20, n – 2)

जैसा कि हम जानते हैं कि, यदि C(n, x) = C(n, y), तो x + y = n।

⇒ (n + 2) + (n – 2) = 20

⇒ 2n = 20

⇒ n = 10

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