Answer
$x^{4}-6x^{2}y+9y^{2}$
Work Step by Step
Step 1: $(x^{2}-3y)^{2}$
Step 2: Using the special product, $(x^{2}-3y)^{2}=(x)^{2}-2(x^{2})(3y)+(3y)^{2}$
Step 3: $(x^{2})^{2}-2(x^{2})(3y)+(3y)^{2}=x^{4}-6x^{2}y+9y^{2}$
Step 4: Therefore, the required answer is $x^{4}-6x^{2}y+9y^{2}$
