Answer:
(y^4+9x^2)(y^2+3x)(y^2-3x)
Step-by-step explanation:
y=-9
-3(y+2)=21
1st Open parenthesis
-3y-6=21
+6 +6
-3y=27
/-3 /-3
I think is 6,-6. Because if you multiply 6×6=36 and -6×-6=36
answer is attached below