Value of $\dfrac{(x-1)^3 + (2x-1)^3 - (3x-2)^3}{(x-1)(2x-1)(3x-2)}$ is equal to:
Step-by-Step Solution
Key Concept: Identity: if $a+b+c=0$ then $a^3+b^3+c^3=3abc$
Step 1: Recognize the algebraic identity for sum of cubes.
We need to evaluate the given expression. Notice that the numerator has the form $a^3 + b^3 + c^3$, which suggests using the algebraic identity: when $a + b + c = 0$, then $a^3 + b^3 + c^3 = 3abc$.
Step 2: Define substitutions to apply the identity.
Let us define:
$$a = x-1$$
$$b = 2x-1$$
$$c = -(3x-2)$$
Step 3: Verify that $a + b + c = 0$.
We compute:
$$a + b + c = (x-1) + (2x-1) + (-(3x-2))$$
$$= x - 1 + 2x - 1 - 3x + 2$$
$$= (x + 2x - 3x) + (-1 - 1 + 2)$$
$$= 0$$
Since the sum equals zero, the identity $a^3 + b^3 + c^3 = 3abc$ applies.
Step 4: Express the numerator using the identity.
The numerator can be rewritten as:
$$(x-1)^3 + (2x-1)^3 - (3x-2)^3 = a^3 + b^3 + c^3$$
Using the identity $a^3 + b^3 + c^3 = 3abc$:
$$a^3 + b^3 + c^3 = 3(x-1)(2x-1)(-(3x-2))$$
$$= -3(x-1)(2x-1)(3x-2)$$
Step 5: Simplify the original expression.
Now we can evaluate the complete expression:
$$\frac{(x-1)^3 + (2x-1)^3 - (3x-2)^3}{(x-1)(2x-1)(3x-2)} = \frac{-3(x-1)(2x-1)(3x-2)}{(x-1)(2x-1)(3x-2)}$$
Canceling the common factor $(x-1)(2x-1)(3x-2)$ from numerator and denominator:
$$= -3$$
**Final Answer:** The value of the expression is $\boxed{-3}$, which corresponds to **Option 1**.
Correct Answer: 4