The results of the analysis are as follows:
- \( \sqrt[3]{(x)} - 3 = y \) is not linear.
- \( 2x - 4y - 6 = 0 \) is linear.
- \( -\sqrt{x}y = 12 \) is not linear.
- \( 2x = y^2 \) is not linear.
Thus, the final answers are:
- For the first equation: \(\boxed{\text{not linear}}\)
- For the second equation: \(\boxed{\text{linear}}\)
- For the third equation: \(\boxed{\text{not linear}}\)
- For the fourth equation: \(\boxed{\text{not linear}}\)