How to find sum of the given infinte series

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In summary, the value of ##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}## is convergent and can be represented as ##A=\sqrt{12+A}##, where A is the limit of the sum and square root infinite times. This can be solved for A to find the value of the expression.
  • #1
22990atinesh
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Homework Statement


The value of ##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}## is

Homework Equations

The Attempt at a Solution


No Clue
 
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  • #2
22990atinesh said:

Homework Statement


The value of ##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}## is

Homework Equations

The Attempt at a Solution


No Clue

Denote the limit when you do the sum and square root infinite times by A.
##A=\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}##.
If you do the same once more, nothing changes
##A=\sqrt{12+A}##.
Solve for A.
 
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  • #3
22990atinesh said:

Homework Statement


The value of ##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}## is

Homework Equations

The Attempt at a Solution


No Clue
Assign the entire sum as a variable.
##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}} = k##
##\Rightarrow 12+\sqrt{12+\sqrt{12+ ...}} = k^2## ... (1)
But,
##\sqrt{12+\sqrt{12+ ...}} = k## ...(2)
Substitute (2) in (1),
Then solve for ##k##.
 
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  • #4
Ashes Panigrahi said:
Assign the entire sum as a variable.
##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}} = k##
##\Rightarrow 12+\sqrt{12+\sqrt{12+ ...}} = k^2## ... (1)
But,
##\sqrt{12+\sqrt{12+ ...}} = k## ...(2)
Substitute (2) in (1),
Then solve for ##k##.

Thnax got it.
 
  • #5
22990atinesh said:

Homework Statement


The value of ##\sqrt{12+\sqrt{12+\sqrt{12+ ...}}}## is

Homework Equations

The Attempt at a Solution


No Clue

Others have already shown you how. However, please realize that the above is not an infinite series. It is an infinite "something", just not a series.
 
  • #6
To be complete you need to show that your expression is convergent.
 

FAQ: How to find sum of the given infinte series

1. What is an infinite series?

An infinite series is a sum of an infinite number of terms. It is written in the form of a_n + a_(n+1) + a_(n+2) + ..., where a_n is the n-th term in the series.

2. How can I find the sum of an infinite series?

There are different methods for finding the sum of an infinite series, depending on the type of series. One common method is to use the formula for the sum of a geometric series, which is given by S = a/(1-r), where S is the sum, a is the first term, and r is the common ratio. Another method is to use the technique of telescoping, where the terms in the series cancel each other out, leaving only a finite number of terms to be added.

3. What is the divergence test for infinite series?

The divergence test is a method used to determine if an infinite series diverges or converges. It states that if the limit of the terms in the series does not approach zero, then the series diverges. However, if the limit is equal to zero, the series may still converge.

4. Can I use a calculator to find the sum of an infinite series?

Yes, there are some calculators that have a function for finding the sum of an infinite series. However, it is important to note that these calculators may not be able to handle all types of series, and it is always recommended to double check the answer using a different method.

5. How can I determine the convergence of an infinite series?

There are several tests that can be used to determine the convergence of an infinite series, such as the comparison test, ratio test, and integral test. These tests compare the given series to a known series or function to determine if it behaves in a similar way. It is important to note that the tests only provide a sufficient condition for convergence, and further analysis may be needed to confirm convergence.

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