Aditya Gupta
Last Activity: 6 Years ago
note that last term of the AP is equal to first term of the GP.
a11= a1+10*2= 20+a1
middle term is a6= a1+5*2
for gp, middle term is a11*2^5= 32a11= 32(20+a1)= a1+5*2
so 31a1=10-640=-630
or a1= -630/31
middle term of entire sequence is 20+a1
20-630/31
-10/31