to expand just go (3x+y)(3x+y)(3x+y)(3x+y) then use something my teacher calls the "crab claw" for just the first 2 brackets by doing 3x*3x + 3x*y + y*3x + y*y to get (9x^2+3xy+3xy+y^2) then find the like terms to get (9x^2+6xy+y^2) which would be the same for the other 2 brackets to get
(9x^2+6xy+y^2) (9x^2+6xy+y^2) then expand them by going 9x^2*9x^2... now you should try the rest. Hope this is the answer you wanted
