Question 271386
{{{(4n)/(n^2- 4) - 2/(n + 2) - 2/(n + 2)}}}
Since subtractions can a source of errors for many people, I am going to start by changing the subtractions into additions:
{{{(4n)/(n^2- 4) + (-2)/(n + 2) + (-2)/(n + 2)}}}
and the last two terms have the same denominator so I will go ahead and add them:
{{{(4n)/(n^2- 4) + (-4)/(n + 2)}}}
To add the remaining fractions we need to get a common denominator first. And to find the Lowest Common Denominator (LCD) we need to factor each denominator:
{{{(4n)/((n+2)(n - 2)) + (-4)/(n + 2)}}}
From this we can see that<ul><li>the LCD is (n+2)(n-2)</li><li>the first fraction already has the LCD as the denominator</li><li>the part of the LCD missing in the second denominator is n-2</li></ul>
So we will multiply the numerator and denominator of the second fraction by n-2:
{{{(4n)/((n+2)(n - 2)) + ((-4)/(n + 2))((n-2)/(n-2))}}}
which simplifies to:
{{{(4n)/((n+2)(n - 2)) + (-4n + 8)/(n + 2)(n-2))}}}
Now we can add the fractions. (Leave the denominators factored for now.):
{{{8/((n+2)(n - 2))}}}
which does not match any of the provided answers. I don't see any errors so I must assume that there is something wrong in the problem you posted. I'm going to guess that the denominator of one of the last two fractions should be n-2 and not n+2. So I am going to solve the problem again with a n-2 denominator. (It doesn't matter which fraction because they are both the same.) I am not going to provide commentary this time. The logic is the same as above except, since the last two fractions no longer have the same denominator to start with, I will not be adding the last two fractions so early.
{{{(4n)/(n^2- 4) - 2/(n + 2) - 2/(n - 2)}}}
{{{(4n)/(n^2- 4) + (-2)/(n + 2) + (-2)/(n - 2)}}}
{{{(4n)/((n+2)(n-2)) + (-2)/(n + 2) + (-2)/(n - 2)}}}
{{{(4n)/((n+2)(n-2)) + ((-2)/(n + 2))((n-2)/(n-2)) + ((-2)/(n - 2))((n+2)/(n+2))}}}
{{{(4n)/((n+2)(n-2)) + (-2n+4)/((n + 2)(n-2)) + (-2n-4)/((n+2)(n-2))}}}
{{{0/((n+2)(n-2))}}}
{{{0}}}
which doesn't match any of the provided answers either. I still see no errors in my work so I have to assume that either the provided answers are in correct or both the original equation and the one I guessed at are also wrong. But perhaps you have seen enough here to figure out the actual problem.