Tag: arithmetic progression

Questions Related to arithmetic progression

Multiple choice maths arithmetic sequences forming an arithmetic progression between two quantities a and b sums arithmetic progression

The sum of the series
$ _{  }^{ 4n }{ { C } _{ 0 } }+ _{  }^{ 4n }{ { C } _{ 4 } }+ _{  }^{ 4n }{ { C } _{ 8 } }+........ _{  }^{ 4n }{ { C } _{ 4n } }$ is 

  1. $2^{4n-2}+(-1)^{n}2^{2n-1}$
  2. $2^{4n-2}+(-1)^{n+1}2^{2n-1}$
  3. $2^{4n-2}-2^{2n-1}$
  4. $2^{4n-2}+2^{2n-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is a standard identity for the sum of binomial coefficients with step 4. The sum of C(4n, 4k) is given by (1/4) * [(1+1)^4n + (1-1)^4n + 2 * (1+i)^4n + 2 * (1-i)^4n]. This simplifies to 2^(4n-2) + 2^(2n-1) * cos(n * pi).

Multiple choice maths arithmetic sequences forming an arithmetic progression between two quantities a and b sums arithmetic progression

Find the sum of 1 + $\dfrac{1}{4} + \dfrac{1.3}{4.8} + \dfrac{1.3.5}{4.8.12} +.......\infty $

  1. $2\sqrt{2}$
  2. $\sqrt{2}$
  3. $\sqrt{2}$
  4. $\sqrt { \frac { 1 }{ 2 } } $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is a binomial expansion (1-x)^(-n). The series 1 + 1/4 + (1*3)/(4*8) + (1*3*5)/(4*8*12) + ... is of the form (1-x)^(-1/2) where x=1/2. Thus, (1 - 1/2)^(-1/2) = (1/2)^(-1/2) = sqrt(2).

Multiple choice maths arithmetic sequences forming an arithmetic progression between two quantities a and b sums arithmetic progression

If  $0 < x , y , a , b < 1 ,$  then the sum of the infinite terms of the series
 $\sqrt { x } ( \sqrt { a } + \sqrt { x } ) + \sqrt { x } ( \sqrt { a b } + \sqrt { x y } ) + \sqrt { x } ( b \sqrt { a } + y \sqrt { x } ) + \ldots$  is

  1. $\dfrac { \sqrt { a x } } { 1 + \sqrt { b } } + \dfrac { x } { 1 + \sqrt { y } }$
  2. $\dfrac { \sqrt { x } } { 1 + \sqrt { b } } + \dfrac { \sqrt { x } } { 1 + \sqrt { y } }$
  3. $\dfrac { \sqrt { x } } { 1 - \sqrt { b } } + \dfrac { \sqrt { x } } { 1 - \sqrt { y } }$
  4. $\dfrac { \sqrt { a x } } { 1 - \sqrt { b } } + \dfrac { x } { 1 - \sqrt { y } }$
Reveal answer Fill a bubble to check yourself
A Correct answer