Can Inequality with Factorial Be Proven without Induction?

In summary, the problem requires proving \frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}<\frac{1}{2n+1} without using induction. The LHS can be rewritten as \frac{(2k-1)!}{(2k)!}, and using the fact that (2k)!=k!2^k and (2k-1)!=\frac{(2k)!}{k!2^k}, we can simplify it to \frac{1}{2^k}, which is less than \frac{1}{2n+1}. Therefore, the inequality is proven
  • #1
cupcakes
18
0

Homework Statement


[itex]\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}<\frac{1}{2n+1}[/itex]

Edit: Must be proven without using induction.

Homework Equations


The Attempt at a Solution


I understand the LHS is the same thing as

[tex]\frac{(2n-1)!}{(2n)!}[/tex]

And (2n)! = [itex]k!2^k[/itex] & (2n-1)! = [itex]\frac{(2k)!}{k!2^k}[/itex]

I've tried substituting and it doesn't seem to help. Any ideas? Thanks.
 
Last edited:
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  • #2
I was able to prove this by induction, try it out!
 
  • #3
cupcakes said:

Homework Statement


[itex]\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}<\frac{1}{2n+1}[/itex]

Homework Equations


The Attempt at a Solution


I understand the LHS is the same thing as

[tex]\frac{(2n-1)!}{(2n)!}[/tex]

And (2n)! = [itex]k!2^k[/itex] & (2n-1)! = [itex]\frac{(2k)!}{k!2^k}[/itex]

I've tried substituting and it doesn't seem to help. Any ideas? Thanks.
There are some typos there.

[itex]\displaystyle (2k)!=k!2^k[/itex]

[itex]\displaystyle (2k-1)!=\frac{(2k-1)!\ (2k)!}{(2k)!}=\frac{(2k)!}{k!2^k}[/itex]
 
  • #4
scurty said:
I was able to prove this by induction, try it out!
I forgot to mention that the problem states that it must be proven without using induction. :(

SammyS said:
There are some typos there.

[itex]\displaystyle (2k)!=k!2^k[/itex]

[itex]\displaystyle (2k-1)!=\frac{(2k-1)!\ (2k)!}{(2k)!}=\frac{(2k)!}{k!2^k}[/itex]

Thanks Sammy :smile:
Does anyone have any other idea or hint that does not involve induction?
 
  • #5
I've solved it. :smile:
 

1. What is "inequality with factorial"?

Inequality with factorial refers to a type of mathematical inequality that involves the use of factorial notation. Factorial notation is denoted by the exclamation mark (!) and is used to represent the product of all positive integers from 1 up to a given number. For example, 5! (read as "five factorial") is equal to 1 x 2 x 3 x 4 x 5 = 120. Inequality with factorial involves comparing two expressions that contain factorial notation.

2. How is inequality with factorial used in mathematics?

Inequality with factorial is commonly used in various mathematical concepts, such as combinatorics, probability, and algebra. It helps in solving problems that involve counting and arranging objects, as well as determining the likelihood of certain events. In algebra, inequality with factorial is used to compare different mathematical expressions and to solve equations involving factorials.

3. What are the properties of inequality with factorial?

The properties of inequality with factorial are similar to those of regular inequalities. For example, multiplying or dividing both sides of an inequality with factorial by a positive number does not change the direction of the inequality, while it does when multiplied or divided by a negative number. In addition, the inequality sign remains the same when both sides of the inequality are raised to an even power, but it changes when raised to an odd power.

4. What are some common mistakes when working with inequality with factorial?

One common mistake when working with inequality with factorial is forgetting to apply the properties of inequality, such as multiplying or dividing by positive or negative numbers. Another mistake is incorrectly evaluating factorials, especially for large numbers, which can lead to incorrect solutions. It is also important to pay attention to the direction of the inequality sign when solving equations involving factorial expressions.

5. How can inequality with factorial be applied in real-life situations?

Inequality with factorial can be applied in various real-life situations, such as in probability and statistics. For example, it can be used to calculate the number of possible outcomes in a game or to determine the probability of winning a lottery. It can also be used in business and economics, such as in calculating the number of possible combinations of products or services and their corresponding profits. Additionally, inequality with factorial can be used in social sciences to analyze and compare different data sets or populations.

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