[tex]( \frac{a}{a - 4} - \frac{a - 4}{a + 4} ) \times \frac{a + 4}{4} = \frac{a(a + 4) - (a - 4) {}^{2} }{(a - 4)(a + 4)} \times \frac{a + 4}{4} = \frac{ {a}^{2} + 4a - (a {}^{2} - 8a + 16) }{4(a - 4)} = \frac{ {a {}^{2} + 4a - a {}^{2} } + 8a - 16}{4(a - 4)} = \frac{12a - 16}{4(a - 4)} = \frac{4(3a - 4)}{4(a - 4)} = \frac{3a - 4}{a - 4} [/tex]