Let a 1 , a 2 , … , a 10 be an A . P . with common difference - 3 and b 1 ,   b 2 , … , b…

Let a1,a2,,a10 be an A.P. with common difference -3 and b1, b2,,b10 be a G.P. with common ratio 2. Let ck=ak+bk, k=1,2,,10. If c2=12 and c3=13, then k=110ck is equal to ______.

Solution

Ck=ak+bk

where ak=a1+(k-1)(-3) and bk=b12k-1

Ck=a1+(k-1)(-3)+b12k-1

k=110ck=k=110ak+k=110bk

C2=a1-3+b1(2)=12   (1)....

C3=a1-6+4 b1=13    (2)......

by solving (1) & (2)
2b1-3=1b1=2 and a1=11

k=110ck=10222+9-3+2210-12-1

=-25+2046=2021

Asked in: JEE Main 2021 (26 Aug Shift 2)

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