Wrong Answer From Calculator for x^2-1 (all over) x+4

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In summary: You had 4a2- 2a- 2a+ 1- 1= 4a2- 4a!f(x) = \frac{x^2-1}{x+4}If x = 2a - 1 then we have: f(2a-1) = \frac{(2a-1)^2-1}{(2a-1) + 4} = \frac{(4a^2 - 4a +1) -1}{2a +3} = \frac{4a^2 - 4a}{2a +3}You could end here or factor out the 4a on the numerator if you really wanted
  • #1
alliecr
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I am not getting the answer that my calculator is giving me for the following:

Find the following values for x^2-1 (all over) x+4

f(2a-1)

I am getting 4a^2 (all over) 2a+3 for my final answer and my calculator is getting (2a-1)^2-1 (all over) 2a+3.

What did I do wrong? Also, how do you work the math latex references?
these:
[x[2]^{}[/tex]-1]\frac{}{}[/x+4]
 
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  • #2
funny. I got x-4+(15)/(x+4)
 
  • #3
Hydrargyrum said:
funny. I got x-4+(15)/(x+4)
Since the answer must have "a" rather that "x" that's not particularly funny!

alliecr said:
I am not getting the answer that my calculator is giving me for the following:

Find the following values for x^2-1 (all over) x+4

f(2a-1)

I am getting 4a^2 (all over) 2a+3 for my final answer and my calculator is getting (2a-1)^2-1 (all over) 2a+3.
Okay, if x= 2a- 1, then x2= (2a-1)2= 4a2- 4a+ 1 so x2- 1= 4a2- 4a. How did you get "4a2"? Also x+ 4= (2a-1)+ 4= 2a+ 3. You have
[tex]\frac{4a^2- 4a+ 1}{2a+ 3}[/ite]

What did I do wrong? Also, how do you work the math latex references?
these:
[x[2]^{}[/tex]-1]\frac{}{}[/x+4]
The [/tex] only ends a latex code. You need [tex] in front. Did you know that you can see the code for a latex formula by clicking on it?
 
  • #4
HallsofIvy said:
Since the answer must have "a" rather that "x" that's not particularly funny!


Okay, if x= 2a- 1, then x2= (2a-1)2= 4a2- 4a+ 1 so x2- 1= 4a2- 4a. How did you get "4a2"? Also x+ 4= (2a-1)+ 4= 2a+ 3. You have
[tex]\frac{4a^2- 4a+ 1}{2a+ 3}[/ite]


The [/tex] only ends a latex code. You need [tex] in front. Did you know that you can see the code for a latex formula by clicking on it?

Where does the+1 come from? I had this before I got my answer: [tex]4a^{2}-2a-2a+1-1...the ones would cancel out right?
 
  • #5
[tex] f(x) = \frac{x^2-1}{x+4}[/tex]
If x = 2a - 1 then we have:
[tex] f(2a-1) = \frac{(2a-1)^2-1}{(2a-1) + 4} = \frac{(4a^2 - 4a +1) -1}{2a +3} = \frac{4a^2 - 4a}{2a +3}[/tex]

You could end here or factor out the 4a on the numerator if you really wanted to.
[tex] \frac{4a(a - 1)}{2a+3}[/tex]
 
  • #6
alliecr said:
Where does the+1 come from? I had this before I got my answer: [tex]4a^{2}-2a-2a+1-1...the ones would cancel out right?
Yes, and I showed that it did. I said (2a-1)2= 4a2- 4a+ 1 so (2a-1)2+ 1= 4a2- 4a just as you have now and just as I had before. But 4a2- 4a is NOT the 4a2 you had before!
 

1. What could cause a wrong answer from a calculator for x^2-1 (all over) x+4?

There could be a few reasons for this. One possibility is that the calculator is using the wrong order of operations, resulting in an incorrect answer. Another possibility is that there is a mistake in the input or the calculator is malfunctioning.

2. How can I fix a wrong answer from a calculator for x^2-1 (all over) x+4?

If the issue is with the order of operations, you can try manually inputting the problem in the correct order. If the issue is with the input or the calculator itself, you may need to double check your inputs and consider using a different calculator or seeking assistance from a teacher or tutor.

3. Is it common for calculators to give wrong answers for x^2-1 (all over) x+4?

It is not common for calculators to give wrong answers, but it can happen. Calculators are electronic devices and can make mistakes, so it is always important to double check the answer and make sure it makes sense in the context of the problem.

4. Are there any known issues with specific calculators and x^2-1 (all over) x+4?

There are not any specific known issues with calculators and this particular problem. However, as mentioned before, mistakes can happen with any calculator, so it's important to always double check your answer.

5. What steps can I take to prevent getting a wrong answer from a calculator for x^2-1 (all over) x+4?

To prevent getting a wrong answer, it is important to make sure you are using the correct order of operations and inputting the problem correctly. You can also double check your answer by using a different calculator or asking for assistance from a teacher or tutor.

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