Limit Problem Solution Explained

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In summary, the solution to the homework equation is to factor out y-1 from the equation and solve for x.
  • #1
joshiemen
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Homework Statement



Lim x>1 (y^1/3-1)/((y^1/5-1)

Homework Equations



Difference of powers a^n-b^n=(a-b)*(a^n-1*b^0+a^n-2*b^1...+b^n-1)

The Attempt at a Solution



Scanned and attached the solution...

Can anyone Pls explain the steps in the solution, especially, how you factor out such an ugly function.
 

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  • #2
[tex]y-1\equiv (y^{1/3})^3-1\equiv (y^{1/n})^n-1[/tex], n being a natural number.

Does this clear things up?
 
  • #3
joshiemen said:

Homework Statement



Lim x>1 (y^1/3-1)/((y^1/5-1)


Homework Equations



Difference of powers a^n-b^n=(a-b)*(a^n-1*b^0+a^n-2*b^1...+b^n-1)


The Attempt at a Solution



Scanned and attached the solution...

Can anyone Pls explain the steps in the solution, especially, how you factor out such an ugly function.

you can actually substitute y=x^15 , as y>1 , x>1
hence obtaining x>1 (x^5-1)/(x^3-1)
try to divide x-1 from top and bottom

There is this identity:
x^n -1 =(x-1)[x^(n-1) + x^(n-2) + ... + 1 ]

Continue from here =D
 
  • #4
icystrike said:
you can actually substitute y=x^15 , as y>1 , x>1
hence obtaining x>1 (x^5-1)/(x^3-1)
try to divide x-1 from top and bottom

There is this identity:
x^n -1 =(x-1)[x^(n-1) + x^(n-2) + ... + 1 ]

Continue from here =D

:) THANK YOU!

Indeed, the joy of understanding is far greater and superior than the earthly pleasures one derives through out his/her life.
 
  • #5
Mentallic said:
[tex]y-1\equiv (y^{1/3})^3-1\equiv (y^{1/n})^n-1[/tex], n being a natural number.

Does this clear things up?

Could you elaborate on this further pls? not so clear, i have been staring at it and thinking, have not penetrated the wall of ignorance yet.
 
  • #6
joshiemen said:
Could you elaborate on this further pls? not so clear, i have been staring at it and thinking, have not penetrated the wall of ignorance yet.

It's essentially the same as icystrike's suggestion.

For [tex]y-1=(y^{1/3})^3-1[/tex] if you substitute [tex]x=y^{1/3}[/tex] or equivalently, [tex]x^3=y[/tex] then we have [tex]x^3-1=(x)^3-1[/tex]

So if you have [tex]y-1[/tex] to factorize this using a difference of two cubes, you substitute [tex]x^3=y[/tex] or if you can see what is happening without substitution, you let [tex]y-1=(y^{1/3})^3-1^3=(y^{1/3}-1)(y^{2/3}+y^{1/3}+1)[/tex]
 

1. What is a limit problem?

A limit problem is a mathematical concept that involves finding the value that a function approaches as its input approaches a specific value. This can help determine the behavior of a function near a particular point.

2. How do you solve a limit problem?

To solve a limit problem, you can use various techniques such as algebraic manipulation, substitution, and using standard limit rules. It is also helpful to graph the function to gain a visual understanding of its behavior near the limit point.

3. What are the common types of limit problems?

The most common types of limit problems include limits at a finite point, limits at infinity, and limits involving trigonometric, exponential, or logarithmic functions.

4. Why are limit problems important?

Limit problems are important because they are used to analyze the behavior of functions, which is crucial in various fields such as physics, engineering, and economics. They also help in determining continuity, differentiability, and the existence of derivatives.

5. Can limit problems have more than one solution?

No, limit problems can only have one solution. The limit of a function is unique at a specific point, and it represents the exact value that the function is approaching. However, different methods can be used to arrive at the same limit value.

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