factor by grouping:

Multiply the
by the
and get
Write down all the pairs of factors of its absolute value,
:
Now since the LAST SIGN in
is MINUS, we SUBTRACT the two
factors in absolute value:
[Note: If the last term had been PLUS, we
would have ADDED the two factors in
absolute value.]
Now we look at the middle term of
,
which is
and we look at the
list of differences and find the
absolute value of
in the next to
last difference,
.
So we substitute
for the 18:
Now we remove the parentheses by distributing:
Factor
out of the first two terms
Factor
out of the last two terms:
Now factor out
Edwin