factor by grouping. there is a common 18x in the first two terms, and a common -9 in the last two

write as

now apply the formula for the difference of two squares factorization

begin by factoring out the common 6

now, what do you aee?

these are one of those two-way quadratic thingys.

here's a tip: forget the y for a while and treat it as

and factor that. when finished, attach a y to the constant terms, and that will take care of the y's in your expression

same advice as the last problem

treat this as

this is a quadratic in

, factor it as you would a quadratic. but instead of

you are using

if it is hard for you to visualize, let

, then you have

. factorize this, and then replace all the

's with

's