Reviewing a Failed Assignment: Evaluating the Limit

In summary, the conversation is about reviewing an assignment that went wrong. The assignment involves evaluating a limit, specifically the limit of (1/2+(x/(x+3))/(x+1) as x approaches -1. The participant initially made a mistake and got x-1/x=2, but they redid the problem and got the correct answer of 3/4 by multiplying both the numerator and denominator by (x+3). They also discuss using LaTeX markup to write equations in the forum.
  • #1
ladyrae
32
0
I’m reviewing an assignment that didn’t go so well

Evaluate limit

lim x->-1 (1/2+(x/(x+3))/(x+1)

I reduced to (1+2x)/2 = -1/2

I originally had x-1/x=2 but i redid the problem as above

Is this correct?
 
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  • #2
No, the answer is 3/4.

[tex]\frac{0.5+\frac{x}{x+3}}{x+1}[/tex]

You want to multiply both the numerator and denominator by x+3 so that you can get rid of the fraction in the numerator. Then it should be easy to factor x+1 out of both the numerator and denominator.
 
Last edited:
  • #3
That's not the correct answer. You want to find:

[tex]
\lim_{x\rightarrow -1} \frac{\frac{1}{2} + \frac{x}{x+3}}{x+1}
[/tex]

Move the (x+1) up into the numerator:

[tex]
\frac{1}{2(x+1)} + \frac{x}{(x+3)(x+1)}
[/tex]

Get a common denominator and add these two terms together, and you should see that the x+1 will fall out of the top and bottom.

Edit: master_coda's way of multiplying the top and bottom by (x+3) is probably simpler.

You should get 3/4, like master_coda said.

Like I said in another of your threads, you can check your work by plugging in a value close to -1 into your original expression (like -0.99999). Your numerical result should be close to the analytical answer. If they aren't, you've probably made a mistake.
 
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  • #4
Notation

I'm a newbie ...

Are you using software to write the equation in that format?
 
  • #5
It's LaTeX markup (code), built into these forums. Check out this thread:

https://www.physicsforums.com/showthread.php?t=8997

The best way to learn is by example. You can click on any equation in any thread and see what the author typed to create it.
 

1. What does it mean to review a failed assignment?

Reviewing a failed assignment means taking a closer look at the assignment that did not meet the desired outcome or expectations. It involves analyzing the mistakes made and understanding what can be improved for future assignments.

2. Why is it important to evaluate the limit when reviewing a failed assignment?

Evaluating the limit is important because it allows us to understand the boundaries of our abilities and where we need improvement. It also helps us to identify any gaps in our knowledge and skills.

3. What are the steps involved in evaluating the limit for a failed assignment?

The steps involved in evaluating the limit for a failed assignment may vary, but generally include: identifying the goal or objective of the assignment, comparing the expected outcome to the actual outcome, analyzing the mistakes made, understanding the underlying concepts and principles, and creating a plan for improvement.

4. How can evaluating the limit help in future assignments?

Evaluating the limit can help in future assignments by providing a clear understanding of where improvements can be made. It also allows us to identify any recurring mistakes or weaknesses, which can be addressed and improved upon for future assignments.

5. Can reviewing a failed assignment be beneficial even if the assignment is not able to be improved?

Yes, reviewing a failed assignment can still be beneficial even if the assignment cannot be improved. It provides an opportunity to reflect on the mistakes made and understand what can be done differently in the future. It also allows for personal growth and learning from the experience.

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