Math Problem Statement

Solution

To evaluate the limit limx15x4xx1\lim_{x \to 1} \frac{\sqrt{5x - 4} - \sqrt{x}}{x - 1}, we'll use algebraic manipulation again. Here are the steps:

  1. Identify the indeterminate form: As x1x \to 1, both the numerator and the denominator approach 0, creating a 00\frac{0}{0} indeterminate form.

  2. Rationalize the numerator: Multiply and divide by the conjugate of the numerator 5x4x\sqrt{5x - 4} - \sqrt{x}, which is 5x4+x\sqrt{5x - 4} + \sqrt{x}.

limx15x4xx15x4+x5x4+x\lim_{x \to 1} \frac{\sqrt{5x - 4} - \sqrt{x}}{x - 1} \cdot \frac{\sqrt{5x - 4} + \sqrt{x}}{\sqrt{5x - 4} + \sqrt{x}}

This transforms the expression into:

limx1(5x4x)(5x4+x)(x1)(5x4+x)\lim_{x \to 1} \frac{(\sqrt{5x - 4} - \sqrt{x})(\sqrt{5x - 4} + \sqrt{x})}{(x - 1)(\sqrt{5x - 4} + \sqrt{x})}

  1. Simplify the numerator: Using the difference of squares formula, a2b2=(ab)(a+b)a^2 - b^2 = (a - b)(a + b), we get:

limx1(5x4)x(x1)(5x4+x)\lim_{x \to 1} \frac{(5x - 4) - x}{(x - 1)(\sqrt{5x - 4} + \sqrt{x})}

This simplifies to:

limx14x4(x1)(5x4+x)\lim_{x \to 1} \frac{4x - 4}{(x - 1)(\sqrt{5x - 4} + \sqrt{x})}

  1. Factor the numerator: The numerator 4x44x - 4 can be factored as 4(x1)4(x - 1):

limx14(x1)(x1)(5x4+x)\lim_{x \to 1} \frac{4(x - 1)}{(x - 1)(\sqrt{5x - 4} + \sqrt{x})}

  1. Cancel common factors: The (x1)(x - 1) terms cancel out:

limx145x4+x\lim_{x \to 1} \frac{4}{\sqrt{5x - 4} + \sqrt{x}}

  1. Evaluate the limit: Substitute x=1x = 1:

45(1)4+1=41+1=41+1=42=2\frac{4}{\sqrt{5(1) - 4} + \sqrt{1}} = \frac{4}{\sqrt{1} + 1} = \frac{4}{1 + 1} = \frac{4}{2} = 2

So, the limit is:

2\boxed{2}

Would you like more details or have any questions?

Here are 5 more questions you might find interesting:

  1. How do you solve limits using L'Hôpital's Rule?
  2. What is the derivative of 5x4\sqrt{5x - 4}?
  3. How do you find the limit of a function involving trigonometric expressions?
  4. Can you explain the Squeeze Theorem with an example?
  5. What are the applications of limits in real-life problems?

Tip: When faced with indeterminate forms like 00\frac{0}{0} or \frac{\infty}{\infty}, consider using algebraic manipulation or L'Hôpital's Rule to simplify the expression before evaluating the limit.