I have this advanced grade 11 factoring question $\displaystyle y^4+2y^2+9$ and i know the answer is $\displaystyle (y^2+3-2y)(y^2+3-2y)$ however I do not know how to get there because when i first factored it i got $\displaystyle y^2(y+1)(y-1)+9$ which is wrong. Any help or tricks are appreciated!

Thanks in advance!