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Let `{a_n}` bc a G.P. such that `a_4/a_6=1/4` and `a_2+a_5=216`. Then `a_1=`A. `12or,(108)/(7)`B. 10C. `7or,(54)/(7)`D. none of these |
Answer» Correct Answer - A Let r be the common ratio of the G.P. Then, `(a_(4))/(a_(6))=(1)/(4)rArr(1)/(r^(2))=(1)/(4)rArrr=pm2` Now, `a_(2)+a_(5)=216` `rArr" "a_(1)(r+r^(4))=216` `rArr" "18a_(1)=216or,14a_(1)=216rArra_(1)=12,(108)/(7)` |
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