Math Problem Statement

Use analytical methods to evaluate each of the following limits. If a limit does not exist, explain why. Assign ∞ or −∞ to the limit where appropriate. lim (√[2 − x] − 1) / [3 − √(4x + 5)] x→1

Solution

We are tasked with evaluating the limit:

limx12x134x+5\lim_{x \to 1} \frac{\sqrt{2 - x} - 1}{3 - \sqrt{4x + 5}}

Step 1: Substitution of x=1x = 1

First, let's substitute x=1x = 1 into the expression to see if we get an indeterminate form or a specific value:

21134(1)+5=1139=1133=00\frac{\sqrt{2 - 1} - 1}{3 - \sqrt{4(1) + 5}} = \frac{\sqrt{1} - 1}{3 - \sqrt{9}} = \frac{1 - 1}{3 - 3} = \frac{0}{0}

Since this results in the indeterminate form 00\frac{0}{0}, we need to apply L'Hopital's Rule or other analytical methods.

Step 2: Apply L'Hopital's Rule

L'Hopital's Rule states that if the limit results in 00\frac{0}{0}, we can differentiate the numerator and the denominator separately and then take the limit again. Let's proceed by differentiating the numerator and denominator.

Numerator: f(x)=2x1f(x) = \sqrt{2 - x} - 1

The derivative of the numerator f(x)=2x1f(x) = \sqrt{2 - x} - 1 is:

f(x)=ddx(2x)=122xf'(x) = \frac{d}{dx} \left( \sqrt{2 - x} \right) = \frac{-1}{2\sqrt{2 - x}}

Denominator: g(x)=34x+5g(x) = 3 - \sqrt{4x + 5}

The derivative of the denominator g(x)=34x+5g(x) = 3 - \sqrt{4x + 5} is:

[ g'(x) = \frac{d}{dx} \left( 3 - \sqrt{4x + 5} \right) = - \frac{4}{2\sqrt{4x + 5}} = \frac{-2}{\sqrt{4x + 5}}

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Math Problem Analysis

Mathematical Concepts

Limits
L'Hopital's Rule
Differentiation
Radical Functions

Formulas

L'Hopital's Rule: If lim f(x)/g(x) results in 0/0 or ∞/∞, lim f'(x)/g'(x)
Derivative of a square root function: d/dx(√u) = u'/2√u

Theorems

L'Hopital's Rule

Suitable Grade Level

Undergraduate Calculus or Advanced High School