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Tq=75 t21=183 find t15 |
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Answer» Answer: Step-by-step explanation: let 9th term be t9 & 21ST term be t21 . TN = a+(n-1)d t9 = a+(9-1)d 75=a+8d ----(1) t21 = a+(21-1)d 183 = a+20d ------(2) substracting eq(1) & (2) we get , 12d=108 d=108/12 d=9 substituting value of d in eq(1) 75=a+8×9 75=a+72 a=75-72 a=3 therefore t81 (81st term ) is t81=a+(81-1)d t81= 3+80×9 t81=3+720 t81 = 723 .. |
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