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If the third and ninth terms area.P are 4 and -8 then which term of thisa.P is zero |
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Answer» Answer: 5th term Step-by-step explanation: nth term = a+(n-1)d 3rd term = a+(3-1)d = a+(2)d = 4 ----(1) 9th term = a+(9-1)d = a+(8)d = -8 ----(2) (1)×4 = 4a+(8)d = 16 (1) - (2) = 3a = 24 =>> a = 8 8+2d = 4 =>> 2d = -4 =>> d = -2 a+(n-1)d = 0 8+(n-1)-2 = 0 (n-1)-2 = -8 (n-1) = 4 n = 4+1 = 5 |
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