Math Problem Statement

on limit

Lim (2x^4 - 2x^3 - x^2 + 1) / (x^4 - x^2 - 2x + 2) as x approaches 1

Solution

The provided image shows the following mathematical expression:

limx12x42x3x2+1x4x22x+2\lim_{{x \to 1}} \frac{2x^4 - 2x^3 - x^2 + 1}{x^4 - x^2 - 2x + 2}

Let's solve this limit step by step.

Step 1: Direct Substitution

First, we'll substitute x=1x = 1 directly into the expression to see if we get a determinate value.

Numerator at x=1:2(1)42(1)3(1)2+1=221+1=0\text{Numerator at } x = 1: 2(1)^4 - 2(1)^3 - (1)^2 + 1 = 2 - 2 - 1 + 1 = 0 Denominator at x=1:(1)4(1)22(1)+2=112+2=0\text{Denominator at } x = 1: (1)^4 - (1)^2 - 2(1) + 2 = 1 - 1 - 2 + 2 = 0

Since both the numerator and the denominator are 00 when x=1x = 1, we have a 00\frac{0}{0} indeterminate form. Therefore, we can apply L'Hôpital's Rule.

Step 2: Apply L'Hôpital's Rule

L'Hôpital's Rule states that for limits of the form 00\frac{0}{0}, we can differentiate the numerator and the denominator separately and then take the limit.

Differentiating the numerator:

ddx(2x42x3x2+1)=8x36x22x\frac{d}{dx} \left( 2x^4 - 2x^3 - x^2 + 1 \right) = 8x^3 - 6x^2 - 2x

Differentiating the denominator:

ddx(x4x22x+2)=4x32x2\frac{d}{dx} \left( x^4 - x^2 - 2x + 2 \right) = 4x^3 - 2x - 2

Step 3: Take the limit again

Now, we take the limit as x1x \to 1 of the new expression:

limx18x36x22x4x32x2\lim_{{x \to 1}} \frac{8x^3 - 6x^2 - 2x}{4x^3 - 2x - 2}

Substitute x=1x = 1:

Numerator: 8(1)36(1)22(1)=862=0\text{Numerator: } 8(1)^3 - 6(1)^2 - 2(1) = 8 - 6 - 2 = 0 Denominator: 4(1)32(1)2=422=0\text{Denominator: } 4(1)^3 - 2(1) - 2 = 4 - 2 - 2 = 0

We still have a 00\frac{0}{0} form, so we apply L'Hôpital's Rule again.

Step 4: Apply L'Hôpital's Rule again

Differentiate the numerator and denominator again.

Second derivative of the numerator:

ddx(8x36x22x)=24x212x2\frac{d}{dx} (8x^3 - 6x^2 - 2x) = 24x^2 - 12x - 2

Second derivative of the denominator:

ddx(4x32x2)=12x22\frac{d}{dx} (4x^3 - 2x - 2) = 12x^2 - 2

Step 5: Take the limit one more time

Now, take the limit as x1x \to 1:

limx124x212x212x22\lim_{{x \to 1}} \frac{24x^2 - 12x - 2}{12x^2 - 2}

Substitute x=1x = 1:

Numerator: 24(1)212(1)2=24122=10\text{Numerator: } 24(1)^2 - 12(1) - 2 = 24 - 12 - 2 = 10 Denominator: 12(1)22=122=10\text{Denominator: } 12(1)^2 - 2 = 12 - 2 = 10

Thus, the limit is:

1\boxed{1}

Final Answer:

The value of the limit is 11.

Would you like further details or have any questions?

Here are 5 related questions to explore:

  1. How does L'Hôpital's Rule work and when can it be applied?
  2. Can L'Hôpital's Rule be applied multiple times?
  3. How do you differentiate polynomials step-by-step?
  4. What other techniques are available for solving indeterminate forms?
  5. How can we evaluate limits without using L'Hôpital's Rule?

Tip: Always check if direct substitution works first when solving limits before applying advanced methods like L'Hôpital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Indeterminate Forms
L'Hôpital's Rule
Polynomial Differentiation

Formulas

L'Hôpital's Rule: lim (f(x)/g(x)) as x approaches c = lim (f'(x)/g'(x)) as x approaches c, for indeterminate forms like 0/0
Polynomial differentiation rules: d/dx [x^n] = nx^(n-1)

Theorems

L'Hôpital's Rule
Rules of Differentiation

Suitable Grade Level

Grades 11-12, College Calculus 1