How do you simplify #(16x^3 - 2y^3)/(16x^3 + 8x^2 y + 4xy^2)#?
You can only cancel if you have factors.
Factorise top and bottom first by taking out the common factor.
THe numerator can be factored further as the difference of cubes:
Now cancel the factors which are the same.
Recall: Difference of cubes: