2) $3 x^{4}-2 x^{3}-6 x+4 \quad L x^{3}-2$
\(\boxed{-2Lx - 6x + 3(Lx - 2)^2 + 8}\) is the final answer
Step 1 :Given the expression: \(3x^4 - 2x^3 - 6x + 4\) and \(x^3 = Lx - 2\)
Step 2 :Substitute \(x^3\) in the expression: \(3(Lx - 2)^4 - 2(Lx - 2)^3 - 6x + 4\)
Step 3 :Simplify the expression: \(-2Lx - 6x + 3(Lx - 2)^2 + 8\)
Step 4 :\(\boxed{-2Lx - 6x + 3(Lx - 2)^2 + 8}\) is the final answer