Question 1176793
<br>
Cross multiplication is not valid here.<br>
If you have an EQUATION of the form a/b=c/d you can cross multiply to get ad=bc.<br>
But there is no equation here (no equals sign).  It's just an expression that is the sum of two fractions.  Simplify by getting a common denominator.<br>
{{{(m+n)/(m-n)+(m-n)/(m+n)}}}<br>
{{{((m+n)(m+n))/((m-n)(m+n))+((m-n)(m-n))/((m+n)(m-n))}}}<br>
{{{(m^2+2mn+n^2)/(m^2-n^2)+(m^2-2mn+n^2)/(m^2-n^2)}}}<br>
{{{(2m^2+2n^2)/(m^2-n^2)}}}<br>