Given f(x)=3xf(x) = 3^{x}f(x)=3x, which of the following is equivalent to f(x+2)−f(x)f(x+2) - f(x)f(x+2)−f(x)?
323^232
8⋅3x8 \cdot 3^x8⋅3x
3x3^x3x
9−3x9 - 3^x9−3x