# Algebra problem (x+(1/x) problem)

• terryds
In summary, using the complex solution of ##\frac{\sqrt{3}-i}{2}##, we can find that ##a^{2016} + (\frac{1}{a})^{2016}## is equal to 2.
terryds

## Homework Statement

If ##a+\frac{1}{a}=\sqrt{3}##, then ##a^{2016} + (\frac{1}{a})^{2016} ## equals

A. 0
B. 1
C. √2
D. √3
E. 2

## The Attempt at a Solution

[/B]
I find no real solution for a.
What I can do is just find a^2 + (1/a)^2 which equals 1, a^4 + (1/a)^4 = -1, a^8 + (1/a)^8 = -1, and so on...
Since 2016 is not a square number, I don't know how to determine the value

Is there any theory about problem like this?

terryds said:

## Homework Statement

If ##a+\frac{1}{a}=\sqrt{3}##, then ##a^{2016} + (\frac{1}{a})^{2016} ## equals

A. 0
B. 1
C. √2
D. √3
E. 2

## The Attempt at a Solution

[/B]
I find no real solution for a.
What I can do is just find a^2 + (1/a)^2 which equals 1, a^4 + (1/a)^4 = -1, a^8 + (1/a)^8 = -1, and so on...
Since 2016 is not a square number, I don't know how to determine the value

Is there any theory about problem like this?
Start from ##a²+1/{a²}=1##.
Multiply by ##a²## to get rid of the denominator, you get ##a^4 +1 =a²##.
Now notice that 2016 is a multiple of 6. So multiply ##a^4 +1 =a²## again by ##a²## to get ##a^6## in the equation.

terryds and SammyS
terryds said:

## The Attempt at a Solution

[/B]
I find no real solution for a.
Find the complex solution. Write it in trigonometric of exponential form, which makes it easy to rise to power 2016. (2016=25*32 *7)

terryds
Samy_A said:
Start from ##a²+1/{a²}=1##.
Multiply by ##a²## to get rid of the denominator, you get ##a^4 +1 =a²##.
Now notice that 2016 is a multiple of 6. So multiply ##a^4 +1 =a²## again by ##a²## to get ##a^6## in the equation.

a^6 + a^2 = a^4
a^6 = a^4 - a^2 = (a^2 - 1) - a^2 = -1
a^12 = 1
a^24 = 1
...
a^2016 = 1

So, 1/a^2016 = 1
a^2016 + (1/a)^2016 = 1 + 1 = 2
Thank you

ehild said:
Find the complex solution. Write it in trigonometric of exponential form, which makes it easy to rise to power 2016. (2016=25*32 *7)

I'm interested to try this approach..

The solution for a is ##\frac{\sqrt{3}\pm i}{2}##
Should I use the plus or the minus as the root?
If it's plus, ##e^{i\frac{1}{6}\pi}##
If it's minus, ##e^{i\frac{11}{6}\pi}##

And, then what should I do??

terryds said:
I'm interested to try this approach..

The solution for a is ##\frac{\sqrt{3}\pm i}{2}##
Should I use the plus or the minus as the root?
If it's plus, ##e^{i\frac{1}{6}\pi}##
If it's minus, ##e^{i\frac{11}{6}\pi}##

And, then what should I do??
What are their 12th power?

ehild said:
What are their 12th power?

The 'plus' root^12 = ##e^{i2\pi}= 1##
The 'minus' root^12 = ##e^{i22\pi} = 1##

Okay, since 2016 can be divided by 12, a^2016 = 1
And 1/a^2016 = 1
So, a^2016 + 1/a^2016 = 1+1 = 2

Thanks a lot!

terryds said:
The 'plus' root^12 = ##e^{i2\pi}= 1##
The 'minus' root^12 = ##e^{i22\pi} = 1##

Okay, since 2016 can be divided by 12, a^2016 = 1
And 1/a^2016 = 1
So, a^2016 + 1/a^2016 = 1+1 = 2

Thanks a lot!
The 'minus' root^12 = ##e^{-i2\pi} = 1##

terryds

## 1. What is the "x+(1/x) problem" in Algebra?

The "x+(1/x) problem" is a type of algebraic expression where a variable, x, is added to the reciprocal of x, which is 1/x. It can also be written as x+1/x.

## 2. How do I solve an "x+(1/x) problem"?

To solve an "x+(1/x) problem", you need to first simplify the expression by finding a common denominator. Then, combine the terms using the rules of addition and subtraction. Finally, solve for the value of x by isolating it on one side of the equation.

## 3. Can an "x+(1/x) problem" have multiple solutions?

Yes, an "x+(1/x) problem" can have multiple solutions. This is because there can be more than one value of x that satisfies the equation. It is important to check your solution by plugging it back into the original equation to ensure it is valid.

## 4. Are there any restrictions on the variable x in an "x+(1/x) problem"?

Yes, there are restrictions on the variable x in an "x+(1/x) problem". Since division by zero is undefined, x cannot be equal to 0. Additionally, if the expression is in the form of x+1/x, x cannot be equal to -1 as this would result in division by zero.

## 5. What real-world applications use the "x+(1/x) problem"?

The "x+(1/x) problem" can be used to solve various real-world problems, such as calculating the total resistance in an electrical circuit or determining the minimum distance between two points on a coordinate plane. It can also be applied in physics, finance, and engineering.

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