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| 1. |
What is common difference between of an A. P. in which a21 - a7 =84 |
| Answer» an=a+(n-1)dFor a21a21=a+(21-1)da21=a+20d-------[1]Now for a7,a7=a+(7-1)da7=a+6d---------[2]a21-(a7)=a+20d-(a+6d) 84 =a+20d-a-6d 84=14d d=84/14 d=6Answer:The common difference of this arithmetic progression is 6. | |