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-81 is the ___term of the AP : 21,18,15 |
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Answer» An=-81. 21,18,15......a=21.d=a2-a1=18-21=-3.An=a+(n-1)d.-81=21+(n-1)(-3).-81=21-3n-3.-81=18-3n.-81-18=-3n.-99=-3n.n=-99/-3.n=33.-81 is 33rd term. a²-a¹=............ a³-a²=............ a⁴-a³=............ a=? And d=? a=21, d=a2-a1 =18-21 =-3an=-81an=a+(n-1) d-81=21+(n-1) -3-81=21-3n+3-81=21+3-3n-81=24-3n-81-24=3n-105=3n-105/3=n-35=n |
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