16-64x(squared) / 8x-4
The first thing I would have done is factor out common numerical factors: 16 divides both 16 and 64: $\displaystyle 16-64x^2= 16(1- 4x^2)$ and 4 divides both 8 and 4: $\displaystyle 8x- 4= 4(2x- 1)$ so the fraction becomes $\displaystyle \frac{16- 64x^2}{8x-4}= \frac{16(1-4x^2)}{4(2x-1)}= 4\frac{1- 4x^2}{2x- 1}= 4\frac{(1- 2x)(1+2x)}{2x-1}$