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In Figure 2 the curve C has equation $y = 6x - x^2$ and the line L has equation $y = 2x$ - Edexcel - A-Level Maths Pure - Question 8 - 2008 - Paper 2

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In Figure 2 the curve C has equation $y = 6x - x^2$ and the line L has equation $y = 2x$. (a) Show that the curve C intersects the x-axis at $x = 0$ and $x = 6$. (... show full transcript

Worked Solution & Example Answer:In Figure 2 the curve C has equation $y = 6x - x^2$ and the line L has equation $y = 2x$ - Edexcel - A-Level Maths Pure - Question 8 - 2008 - Paper 2

Step 1

Show that the curve C intersects the x-axis at $x = 0$ and $x = 6$.

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Answer

To find the x-intercepts of the curve C, we set y=0y = 0 in the equation of the curve:

6xx2=06x - x^2 = 0

Factoring the equation gives:

x(6x)=0x(6 - x) = 0

This gives the solutions:

  1. x=0x = 0
  2. 6x=0x=66 - x = 0 \Rightarrow x = 6

Hence, the curve C intersects the x-axis at the points (0,0)(0, 0) and (6,0)(6, 0).

Step 2

Show that the line L intersects the curve C at the points $(0, 0)$ and $(4, 8)$.

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Answer

To find the intersection points, we set the equations of the curve and the line equal to each other:

6xx2=2x6x - x^2 = 2x

Rearranging gives:

x24x=0x^2 - 4x = 0

Factoring:

x(x4)=0x(x - 4) = 0

Thus, the solutions are:

  1. x=0x = 0
  2. x=4x = 4

Now, substituting x=4x = 4 back into either equation to find y:

y=2(4)=8y = 2(4) = 8

Therefore, the intersections are (0,0)(0, 0) and (4,8)(4, 8).

Step 3

Use calculus to find the area of R.

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Answer

To find the area of region R, we need to integrate the difference between the upper curve C and the lower line L from x=0x = 0 to x=4x = 4:

Area=04(6xx2)(2x)dx\text{Area} = \int_{0}^{4} (6x - x^2) - (2x) \, dx

Simplifying the integrand gives:

Area=04(4xx2)dx\text{Area} = \int_{0}^{4} (4x - x^2) \, dx

Calculating the integral:

=[2x2x33]04= \left[ 2x^2 - \frac{x^3}{3} \right]_{0}^{4}

Evaluating at the bounds:

=(2(4)2(4)33)(00)= \left( 2(4)^2 - \frac{(4)^3}{3} \right) - \left( 0 - 0 \right)
=(32643)=96643=323= \left( 32 - \frac{64}{3} \right) = \frac{96 - 64}{3} = \frac{32}{3}

Thus, the area of region R is rac{32}{3} square units.

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