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Let `a_(n)` be the nth term of an AP, if `sum_(r=1)^(100)a_(2r)=alpha " and "sum_(r=1)^(100)a_(2r-1)=beta`, then the common difference of the AP isA. `alpha-beta`B. `beta-alpha`C. `(alpha-beta)/(2)`D. None of these |
Answer» Correct Answer - D Given that, `sum_(r=1)^(100)a_(2r)=alpha` ` implies a_(2)+a_(4)+"....."+a_(200)=alpha" " "....(i)"` and `sum_(r=1)^(100)a_(2r-1)=beta` `implies a_(1)+a_(3)+"......"+a_(199)=beta " " "………(ii)"` On subtracting Eq.(ii) from Eq.(i), we get ` (a_(2)-a_(1))+(a_(4)-a_(3))+"......."+(a_(200)-a_(199))=alpha -beta` `d+d+"......"` upto 100 terms `=alpha -beta` [beacause `a_(n)` be the nth term of AP with common difference d] `100d=alpha-beta` `d=(alpha-beta)/(100)`. |
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