Let {t}_{p}&{t}_{q} is the {p}^{th}&{q}^{th}terms of the series −16,8,−4,2,...
Here a=−16,r=−21
Then, tp=−16(−21)p−1
tq=−16(−21)q−1
The roots of the given quadratic equation 4x2−9x+5=0 is x=1,45.
AM=45,GM=1(∵AM≥GM)
Now, given 45=2tp+tq,1=tptq
So, 1=256(−21)p+q−2⇒2p+q−2=(−1)p+q−228
⇒2p+q−10=(−1)p+q−2
It is equal when 2p+q−10=1=(−1)p+q−2
Hence, p+q−10=0⇒p+q=10