Let a_1, a_2, a_3, ldots be in an arithmetic | vedclass

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Question

$ \mathrm{d} ightarrow 	ext { common diff. } $

$ \mathrm{A}_{\mathrm{k}}=-\mathrm{kd}[2 \mathrm{a}+(2 \mathrm{k}-1) \mathrm{d}] $

$ \mathrm{A

Vedclass · Accepted Answer

$910$

Vedclass · Answer

$ \mathrm{d} ightarrow 	ext { common diff. } $

$ \mathrm{A}_{\mathrm{k}}=-\mathrm{kd}[2 \mathrm{a}+(2 \mathrm{k}-1) \mathrm{d}] $

$ \mathrm{A}_3=-153 $

$ \Rightarrow 153=13 \mathrm{~d}[2 \mathrm{a}+5 \mathrm{~d}] $

$ 51=\mathrm{d}[2 \mathrm{a}+5 \mathrm{~d}] $

$ \mathrm{A}_5=-435 $

$ 435=5 \mathrm{~d}[2 \mathrm{a}+9 \mathrm{~d}] $

$ 87=\mathrm{d}[2 \mathrm{a}+9 \mathrm{~d}] $

$ (2)-(1) $

$ 36=4 \mathrm{~d}^2$

$ \mathrm{~d}=3, \mathrm{a}=1 $

$ \mathrm{a}_{17}-\mathrm{A}_7=49-[-7.3[2+39]]=910$

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