a) \frac{4x^{2} - a^{2}}{2x - a} = \frac{(2x + a)(2x - a)}{2x - a} = 2x + a
c) \frac{x^{2} + 3x}{x^{3} + 27} = \frac{x(x + 3)}{x^{3} + 27} = \frac{x(x + 3)}{(x + 3)(x^{2} - 3x + 9)} = \frac{x}{x^{2} - 3x + 9}
a) \frac{4x^{2} - a^{2}}{2x - a} = \frac{(2x + a)(2x - a)}{2x - a} = 2x + a
c) \frac{x^{2} + 3x}{x^{3} + 27} = \frac{x(x + 3)}{x^{3} + 27} = \frac{x(x + 3)}{(x + 3)(x^{2} - 3x + 9)} = \frac{x}{x^{2} - 3x + 9}