Question 128521

1. Factor a -4 out of the numerator:
{{{(12 - 4a)= -4(-3 + a) = -4(a - 3)}}}
2. Factor a 2 out of the denominator:
{{{(2a^2 - 18) = 2(a^2 - 9)}}}
3. {{{a^2 - 9}}} is the difference of two perfect squares so we can use the formula: {{{(x^2 - y^2) = (x - y)*(x + y)}}}
Therefore:
{{{(a^2 - 9) = (a - 3)* (a + 3)}}}
4. Our expression is now:
{{{-4(a - 3)/((2)*(a - 3)*(a + 3))}}}
5. Simplify by
a) cancelling out the (a - 3) term
b) dividing 2 out of both numerator and denominator
6. We are left with:
{{{-2/(a + 3)}}}
You were close!