Notice that you have denominators
and . These are
called "reversed differences".
This is how we treat this: Take the
one which is not in descending order
write it in descending order:
factor out , which changes
both signs:
or just
Now substitute that for:
Cancel the negative sign on the
bottom of the second fraction with
the minus sign in front of the
second fraction,making it a plus
in front of the second fraction:
Now the denominators are the same,
so all we need do is combine the
two numerators over their common
denominator:
or
Edwin
