Having a Derp moment.

Alright, so I'm doing some Intermediate algebra, specifically simplifying factors, and I completely forgot if it's allowed to cross out denominators that are next to each other.

i.e.

3x(x)                            x
_____              ---     ________
(3x+4)(3x-4)           3x+4

Would it be possible to cross out the 3x+4's?