Question 74723
Let a=first # and b=2nd #
If the length is the sum of the numbers then
{{{L=a+b}}}
And if the width is the difference of the 2 then
{{{w=(a-b)}}}
So the area is 
{{{A=L*w=(a+b)*(a-b)=a^2+cross(ab-ab)+b^2=a^2-b^2}}}
So the area is 
{{{A=a^2-b^2}}}