Answer: 3x²-3y²+8xy
Step-by-step explanation:
When you multiply two factors, you want to use the FOIL method.
First
Outer
Inner
Last
(x+3y)(3x-y) [distribute by FOIL]
3x²-xy+9xy-3y² [combine like terms]
3x²+8xy-3y² [rewrite]
3x²-3y²+8xy
Now, we know the product is 3x²-3y²+8xy.
