The value of lim_{x→2} [1/(x−2) − 2(2x−3)/(x³−3x²+2x)] equals:
Step-by-Step Solution
Key Concept: Algebraic simplification of limits by factoring
Step 1: Factor the denominator of the second fraction.
We need to simplify the denominator $x^3 - 3x^2 + 2x$. First, factor out $x$:
$$x^3 - 3x^2 + 2x = x(x^2 - 3x + 2)$$
Now factor the quadratic $x^2 - 3x + 2$:
$$x^2 - 3x + 2 = (x-1)(x-2)$$
Therefore:
$$x^3 - 3x^2 + 2x = x(x-1)(x-2)$$
Step 2: Rewrite the original expression with the factored denominator.
The limit becomes:
$$\lim_{x \to 2} \left[\frac{1}{x-2} - \frac{2(2x-3)}{x(x-1)(x-2)}\right]$$
Step 3: Combine the fractions over a common denominator.
The common denominator is $x(x-1)(x-2)$. Rewrite the first fraction:
$$\frac{1}{x-2} = \frac{x(x-1)}{x(x-1)(x-2)}$$
Now combine:
$$\frac{x(x-1) - 2(2x-3)}{x(x-1)(x-2)}$$
Step 4: Simplify the numerator.
Expand the numerator:
$$x(x-1) - 2(2x-3) = x^2 - x - 4x + 6 = x^2 - 5x + 6$$
Factor this quadratic:
$$x^2 - 5x + 6 = (x-2)(x-3)$$
Step 5: Cancel the common factor and simplify.
The expression becomes:
$$\frac{(x-2)(x-3)}{x(x-1)(x-2)} = \frac{x-3}{x(x-1)}$$
The factor $(x-2)$ cancels out, and the expression is now defined at $x = 2$.
Step 6: Evaluate the limit.
Substitute $x = 2$ into the simplified expression:
$$\lim_{x \to 2} \frac{x-3}{x(x-1)} = \frac{2-3}{2(2-1)} = \frac{-1}{2 \cdot 1} = -\frac{1}{2}$$
**Final Answer:** The value of the limit is $-\dfrac{1}{2}$, which corresponds to **Option 3**.
Correct Answer: 3