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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 points where the curve intersects the x-axis, we set y=0y = 0 in the equation of the curve C:

6xx2=06x - x^2 = 0

Factoring out x:

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

This gives us the solutions x=0x = 0 and x=6x = 6. Therefore, 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 line L and the curve C equal to each other:

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

Rearranging gives:

x24x=0x^2 - 4x = 0

Factoring out xx:

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

Thus, x=0x = 0 or x=4x = 4. For x=0x = 0, substituting back, we find the point (0,0)(0, 0).

For x=4x = 4:

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

Therefore, the points of intersection 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 set up an integral between the intersection points.

The area AA can be computed as:

A=04(6xx2)(2x)dx A = \int_0^4 (6x - x^2) - (2x) \, dx

Which simplifies to:

A=04(4xx2)dx A = \int_0^4 (4x - x^2) \, dx

Calculating the integral:

A=[2x2x33]04 A = \left[2x^2 - \frac{x^3}{3}\right]_0^4

Evaluating at the bounds:

A=(2(42)(4)33)0=32643=96643=323 A = \left(2(4^2) - \frac{(4)^3}{3}\right) - 0 = 32 - \frac{64}{3} = \frac{96 - 64}{3} = \frac{32}{3}

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

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