Math Problem Statement

the curve with equation y=8x^2 + 2/x find the co-ordinate of this stationary point. Show your working clearly.

Solution

To find the coordinates of the stationary point on the curve y=8x2+2xy = 8x^2 + \frac{2}{x}, we need to determine the points where the derivative dydx\frac{dy}{dx} is zero.

Step 1: Differentiate the equation

The given equation is: y=8x2+2xy = 8x^2 + \frac{2}{x}

Let's find dydx\frac{dy}{dx}:

  1. Differentiate 8x28x^2 with respect to xx: ddx(8x2)=16x\frac{d}{dx}(8x^2) = 16x

  2. Differentiate 2x\frac{2}{x} with respect to xx: ddx(2x)=2x2\frac{d}{dx}\left(\frac{2}{x}\right) = -\frac{2}{x^2}

So, dydx=16x2x2\frac{dy}{dx} = 16x - \frac{2}{x^2}

Step 2: Set the derivative to zero to find stationary points

To find the stationary points, set dydx=0\frac{dy}{dx} = 0: 16x2x2=016x - \frac{2}{x^2} = 0

Multiply both sides by x2x^2 to eliminate the fraction: 16x32=016x^3 - 2 = 0

Rearrange to solve for xx: 16x3=216x^3 = 2 x3=216x^3 = \frac{2}{16} x3=18x^3 = \frac{1}{8}

Taking the cube root of both sides: x=12x = \frac{1}{2}

Step 3: Substitute x=12x = \frac{1}{2} back into the original equation to find yy

Now that we know x=12x = \frac{1}{2}, substitute it into the original equation to find yy: y=8(12)2+212y = 8\left(\frac{1}{2}\right)^2 + \frac{2}{\frac{1}{2}}

Calculate each term separately:

  1. 8(12)2=814=28\left(\frac{1}{2}\right)^2 = 8 \cdot \frac{1}{4} = 2
  2. 212=2×2=4\frac{2}{\frac{1}{2}} = 2 \times 2 = 4

So, y=2+4=6y = 2 + 4 = 6

Conclusion

The coordinates of the stationary point are: (12,6)\left( \frac{1}{2}, 6 \right)

Would you like further explanation or have any questions?


Here are some related questions:

  1. How do we determine the nature of the stationary point?
  2. What happens if we differentiate the function again to find concavity?
  3. Could we use a graphical approach to verify the stationary point?
  4. What are the implications of stationary points in real-world applications?
  5. How can we find other features of the curve, like asymptotes?

Tip: Checking the second derivative can help you determine whether a stationary point is a maximum, minimum, or a point of inflection.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Stationary Points
Derivatives

Formulas

y = 8x^2 + 2/x
dy/dx = 16x - 2/x^2

Theorems

Derivative test for stationary points
Setting the derivative equal to zero

Suitable Grade Level

Grades 11-12