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Ex 7.4, 1 If nC8 = nC2, find nC2 . Given nC8 = nC2 If nCr = nCp then either r = p or r = n – p Thus, nC8 = nC2 8 = n – 2 8 + 2 = n 10 = n n = 10 Calculating nC2 Putting n = 10 10C2 = 10!/2!(10 βˆ’ 2)! = 𝟏𝟎!/(𝟐! πŸ–!) = (10 Γ— 9 Γ— 8!)/((2 Γ— 1)Γ— 8!) = (10 Γ— 9)/2 = 45

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.