## Algebra: A Combined Approach (4th Edition)

$9x^{2}-6xy+y^{2}$
Using the square of the binomial $(a-b)^{2}=a^{2}-2ab+b^{2}$, $(3x-y)^{2}=(3x)^{2}-2(3x)(y)+y^{2}=9x^{2}-6xy+y^{2}$.