To factor the expression \(3x^3 + 12x^2 + 18x\) completely, we can start by factoring out the common factor.
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Identify the common factor: The common factor in the expression is \(3x\).
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Factor out \(3x\): \[ 3x^3 + 12x^2 + 18x = 3x(x^2 + 4x + 6) \]
Now we have factored the original expression into \(3x(x^2 + 4x + 6)\).
Now, we need to check if \(x^2 + 4x + 6\) can be factored further. To do this, we can calculate its discriminant:
\[ \text{Discriminant} = b^2 - 4ac = 4^2 - 4 \cdot 1 \cdot 6 = 16 - 24 = -8 \]
Since the discriminant is negative, \(x^2 + 4x + 6\) has no real roots and cannot be factored over the real numbers.
So the complete factorization of \(3x^3 + 12x^2 + 18x\) is: \[ \boxed{3x(x^2 + 4x + 6)} \]