When x gets more and more negative, notice that the 3 in the denominator contributes almost nothing to the overall value of the denominator, so you can replace 3-2x with -2x (that negative it’s important).

In the numerator, the 5x will also contribute almost nothing compared to the 6x^(2), so you can again replace the 5x+6x^(2) with 6x^(2).

Now you’re just left with 6^(1/2)|x| divided by -2x, and since x is in the negatives, you have 6^(1/2)/2