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| 1. |
In an AP. a=8, an=62, sn=210 find n and d |
| Answer» an=a+(n-1)d62=8+(n_1)d54=nd-d (1)Sn=n/2 (2a+(n-1)d)210=n/2 (2×8+(n-1)d)420=n (16+nd-d )420=16n+n (nd-d )420=16n+n (54) (from 1)420=16n+54n420=70n420/70=nHence n=6 Now put the value of n in equation 1,we get54=nd-d 54=6d-d54/5=d | |