Question 64937
If you had to do the problem 1/2 - 1/3 you would need to find a common denominator. The easiest way is to do 2 x 3 = 6. This approach doesn't guarantee the Lowest common denominator but it always gives a common denominator.

In this example
{{{2/(5w+10) - 3/(2w-4)}}}
Factorise the bottom numbers as much as possible.
{{{2/(5(w+2)) - 3/(2(w-2))}}}
A common denominator is found by multiplying 5 x (w+2) x 2 x (w-2)
{{{2/(5(w+2))*2(w-2)/(2(w-2)) - 3/(2(w-2))*5(w+2)/(5(W+2))}}}
{{{(2*2(w-2)- 3*5(w+2))/(5(w+2)2(w-2))}}}
{{{(4w-8-(15w+30))/(5(w+2)2(w-2))}}}
{{{(4w-8-15w-30)/(5(w+2)2(w-2))}}}
{{{(-11w-38)/(5(w+2)2(w-2))}}}
{{{(-11w-38)/(10(w+2)(w-2))}}}