Math Problem Statement

The following limit lim x→0+ x ln(4x2).

Solution

We are tasked with evaluating the following limit:

limx0+xln(4x2)\lim_{x \to 0^+} x \ln(4x^2)

Step 1: Simplifying the Expression

We can start by simplifying the logarithmic term:

ln(4x2)=ln(4)+ln(x2)=ln(4)+2ln(x)\ln(4x^2) = \ln(4) + \ln(x^2) = \ln(4) + 2\ln(x)

So, the limit becomes:

limx0+x(ln(4)+2ln(x))\lim_{x \to 0^+} x \left( \ln(4) + 2\ln(x) \right)

Distribute xx:

limx0+(xln(4)+2xln(x))\lim_{x \to 0^+} \left( x \ln(4) + 2x \ln(x) \right)

Step 2: Evaluating Each Term

  1. Term 1: xln(4)x \ln(4)

Since ln(4)\ln(4) is a constant, this term behaves as:

limx0+xln(4)=0\lim_{x \to 0^+} x \ln(4) = 0

  1. Term 2: 2xln(x)2x \ln(x)

This term requires more careful handling. As x0+x \to 0^+, we need to determine the behavior of xln(x)x \ln(x). Notice that ln(x)\ln(x) becomes very negative as xx approaches 0 from the right. Let's evaluate this term using L'Hopital's Rule, since it has the indeterminate form 0×()0 \times (-\infty).

Rewriting it as:

limx0+2xln(x)=limx0+2ln(x)1/x\lim_{x \to 0^+} 2x \ln(x) = \lim_{x \to 0^+} \frac{2 \ln(x)}{1/x}

Now, apply L'Hopital's Rule (which is applicable for indeterminate forms of type \frac{-\infty}{\infty}):

Differentiate the numerator and denominator:

  • Derivative of 2ln(x)2 \ln(x) is 2x\frac{2}{x}
  • Derivative of 1/x1/x is 1x2-\frac{1}{x^2}

Applying L'Hopital's Rule:

limx0+2/x1/x2=limx0+2x=0\lim_{x \to 0^+} \frac{2/x}{-1/x^2} = \lim_{x \to 0^+} -2x = 0

Thus, the second term limx0+2xln(x)=0\lim_{x \to 0^+} 2x \ln(x) = 0.

Step 3: Conclusion

Both terms tend to 0, so:

limx0+xln(4x2)=0\lim_{x \to 0^+} x \ln(4x^2) = 0

Final Answer:

0\boxed{0}


Would you like more details on L'Hopital's Rule or the behavior of logarithmic functions near zero? Here are some related questions:

  1. How does L'Hopital's Rule work with limits of the form 0×0 \times \infty?
  2. What is the behavior of xln(x)x \ln(x) as x0+x \to 0^+?
  3. What happens when we have limits involving other logarithmic functions, like ln(xn)\ln(x^n)?
  4. How does logarithmic growth compare to polynomial or exponential growth as xx approaches 0 or infinity?
  5. Can we apply L'Hopital's Rule to limits involving trigonometric functions?

Tip: When encountering logarithmic limits like xln(x)x \ln(x), it's often useful to rewrite the expression in a form suitable for L'Hopital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Logarithmic Functions
L'Hopital's Rule

Formulas

ln(a*b) = ln(a) + ln(b)
ln(x^n) = n * ln(x)
L'Hopital's Rule: If a limit has indeterminate forms like 0/0 or ∞/∞, then lim x→c f(x)/g(x) = lim x→c f'(x)/g'(x) (if the derivative limits exist)

Theorems

L'Hopital's Rule

Suitable Grade Level

Grades 11-12 or early college