Math Problem Statement

The equation of a curve is y = sqrt(2x - 1) / x. Calculate the gradient of the tangents to the curve at the point where x = 1.

Solution

We are tasked to calculate the gradient of the tangents to the curve at x=1x = 1, where the curve is defined as:

y=2x1x.y = \frac{\sqrt{2x - 1}}{x}.

To find the gradient, we need to:

  1. Differentiate yy with respect to xx.
  2. Evaluate the derivative at x=1x = 1.

Step 1: Differentiate y=2x1xy = \frac{\sqrt{2x - 1}}{x}

Using the quotient rule for differentiation:

ddx(uv)=vdudxudvdxv2,\frac{d}{dx}\left(\frac{u}{v}\right) = \frac{v \frac{du}{dx} - u \frac{dv}{dx}}{v^2},

where:

  • u=2x1u = \sqrt{2x - 1},
  • v=xv = x.

Differentiate uu and vv:

  • dudx=ddx2x1=122x12=12x1\frac{du}{dx} = \frac{d}{dx} \sqrt{2x - 1} = \frac{1}{2\sqrt{2x - 1}} \cdot 2 = \frac{1}{\sqrt{2x - 1}},
  • dvdx=1\frac{dv}{dx} = 1.

Substitute into the quotient rule:

dydx=x12x12x11x2.\frac{dy}{dx} = \frac{x \cdot \frac{1}{\sqrt{2x - 1}} - \sqrt{2x - 1} \cdot 1}{x^2}.

Simplify: dydx=x2x12x1x2.\frac{dy}{dx} = \frac{\frac{x}{\sqrt{2x - 1}} - \sqrt{2x - 1}}{x^2}.

Combine the terms in the numerator under a common denominator: dydx=x(2x1)2x1x2.\frac{dy}{dx} = \frac{\frac{x - (2x - 1)}{\sqrt{2x - 1}}}{x^2}.

Simplify further: dydx=x+12x1x2.\frac{dy}{dx} = \frac{\frac{-x + 1}{\sqrt{2x - 1}}}{x^2}.

This becomes: dydx=1xx22x1.\frac{dy}{dx} = \frac{1 - x}{x^2 \sqrt{2x - 1}}.

Step 2: Evaluate the derivative at x=1x = 1

Substitute x=1x = 1 into the derivative: dydx=11122(1)1=011=0.\frac{dy}{dx} = \frac{1 - 1}{1^2 \sqrt{2(1) - 1}} = \frac{0}{1 \cdot \sqrt{1}} = 0.

Final Answer:

The gradient of the tangent to the curve at x=1x = 1 is:

0.\boxed{0}.

Let me know if you'd like more details or have any other questions!


Related Questions:

  1. How is the quotient rule derived?
  2. Why does the numerator 1x1 - x simplify to zero at x=1x = 1?
  3. What happens to the curve when x<12x < \frac{1}{2}, and why is 2x1\sqrt{2x - 1} undefined there?
  4. How can you confirm the gradient calculation graphically?
  5. What is the physical meaning of a gradient of zero in this context?

Tip: Always check the domain of the function before differentiating; in this case, 2x102x - 1 \geq 0, so x12x \geq \frac{1}{2}.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Quotient Rule
Simplification of Derivatives

Formulas

Quotient Rule: (d/dx)(u/v) = (v * (du/dx) - u * (dv/dx)) / v^2
Derivative of sqrt(f(x)): d/dx sqrt(f(x)) = (1 / 2sqrt(f(x))) * f'(x)

Theorems

Quotient Rule

Suitable Grade Level

Grade 12 or introductory calculus course