HARD
JEE Main
IMPORTANT
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Let A1,A2,A3 be the three A.P. with the same common difference d and having their first terms as A,A+1, A+2, respectively. Let a,b,c be the 7th ,9th ,17th  terms of A1, A2, A3, respectively such that a712b171c171+70=0. If a=29, then the sum of first 20 terms of an AP whose first term is c-a-b and common difference is d12, is equal to _____ .

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Important Questions on Sequences and Series

HARD
JEE Main
IMPORTANT
For the two positive numbers a,b, if a,b and 118 are in a geometric progression, while 1a,10 and 1 b are in an arithmetic progression, then, 16a+12b is equal to _____ .
EASY
JEE Main
IMPORTANT
Let a1,a2,a3,. be a GP of increasing positive numbers. If the product of fourth and sixth terms is 9 and the sum of fifth and seventh terms is 24 , then a1a9+a2a4a9+a5+a7 is equal to
HARD
JEE Main
IMPORTANT

Let a1=b1=1 and an=an-1+(n-1),bn=bn-1+ an-1,n2. If S=n=110bn2n and T=n=18n2n-1 then 27(2S-T)  is equal to

HARD
JEE Main
IMPORTANT
Let $\left\{a_k\right\}$ and $\left\{b_k\right\}, k \in \mathbb{N}$, be two G.P.s with common ratio $r_1$ and $r_2$ respectively such that $\mathrm{a}_1=\mathrm{b}_1=4$ and $\mathrm{r}_1<\mathrm{r}_2$. Let $\mathrm{c}_{\mathrm{k}}=\mathrm{a}_{\mathrm{k}}+\mathrm{b}_{\mathrm{k}}, \mathrm{k} \in \mathbb{N}$. If $\mathrm{c}_2=5$ and $\mathrm{c}_3=\frac{13}{4}$ then $\sum_{\mathrm{k}=1}^{\infty} \mathrm{c}_{\mathrm{k}}-\left(12 \mathrm{a}_6+8 \mathrm{~b}_4\right)$ is equal to
HARD
JEE Main
IMPORTANT
n=0n3((2n)!)+(2n-1)(n!)(n!)((2n)!)=ae+be+c where   a, b, c   and  e=n=01n!  Then a2-b+c is  equal to _______
EASY
JEE Main
IMPORTANT
Let a,b,c>1,a3,b3 and c3 be in A.P. and logab, logca and logbc be in G.P. If the sum of first 20 terms of an A.P., whose first term is a+4b+c3 and the common difference is a-8b+c10 is -444, then abc is equal to
EASY
JEE Main
IMPORTANT

The 8th  common term of the series
S1=3+7+11+15+19+

S2=1+6+11+16+21+. is