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If 6th term and 17th term of an A.P 19 and 41find common difference first term 40th term |
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Answer» t6 = a + (n-1)d 19 = a + 5d -(i)t17 = a + (n-1)d 41 = a + 16d -(II)solving equations (i) & (ii)=> a + 16d = 41 a + 5d = 19 ×(-)=> a + 16d = 41 - a - 5d = -19=> 11d = 22=> d = 2substituting d = 2 in EQUATION (i)=> a + 5(2) = 19=> a = 9t40 = a + (n-1)d = 9 + 39(2) = 9 + 78 = 87 |
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