Answer:
[tex]9x^{2} -6xy-3y^{2}[/tex]
Step-by-step explanation:
[tex](3x+y)(3x+-3y)[/tex]
[tex](3x)(3x)+(3x)(-3y)+(y)(3x)+(y)(-3y)[/tex]
[tex]9x^{2} -9xy+3xy-3y^{2}[/tex]
9xsq - 6xy -3ysq
3x x 3x = 9xsq
3x x -3y= -9xy
y x 3x = 3xy
y x -3y= -3ysq
9xsq -9xy +3xy -3ysq
9xsq -6xy - 3ysq
sq = squared
