Final answer:
To simplify the given expression, factor and cancel out common terms to get the final simplified expression as -8(3y + x) / 3.
Step-by-step explanation:
To simplify the expression, we need to factor and cancel out common terms. Let's break down the steps:
- Factor the numerators and denominators:
 (6x^2 - 8) = 2(3x^2 - 4)
 (36y^2 - 4x^2) = 4(9y^2 - x^2)
 (9x^2 - 12) = 3(3x^2 - 4)
- Cancel out common terms:
 2 and 4 cancel out
 (3x^2 - 4) and (3x^2 - 4) cancel out
- The final simplified expression is:
 -8(3y + x) / 3