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The diagram shows part of the curve with equation $y = x^3 - 2x^2 - 4x + 1$ and the line with equation $y = x - 5$ - Scottish Highers Maths - Question 8 - 2023

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Question 8

The-diagram-shows-part-of-the-curve-with-equation-$y-=-x^3---2x^2---4x-+-1$-and-the-line-with-equation-$y-=-x---5$-Scottish Highers Maths-Question 8-2023.png

The diagram shows part of the curve with equation $y = x^3 - 2x^2 - 4x + 1$ and the line with equation $y = x - 5$. The curve and the line intersect at the points w... show full transcript

Worked Solution & Example Answer:The diagram shows part of the curve with equation $y = x^3 - 2x^2 - 4x + 1$ and the line with equation $y = x - 5$ - Scottish Highers Maths - Question 8 - 2023

Step 1

Integrate using "upper - lower"

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Answer

To find the shaded area between the curve and the line, we need to evaluate the integral of the difference between the two functions from their intersection points, which are given as x=2x = -2 and x=1x = 1.

We will calculate: extArea=21((x5)(x32x24x+1))dx ext{Area} = \int_{-2}^{1} ((x - 5) - (x^3 - 2x^2 - 4x + 1)) \, dx

Step 2

Identify limits

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Answer

The limits of integration are set from x=2x = -2 to x=1x = 1.

Step 3

Integrate both functions

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Answer

Now we simplify the integrand: (x5)(x32x24x+1)=x3+2x2+54x(x - 5) - (x^3 - 2x^2 - 4x + 1) = -x^3 + 2x^2 + 5 - 4x

Thus, the integral becomes: 21(x3+2x24x+4)dx\int_{-2}^{1} (-x^3 + 2x^2 - 4x + 4) \, dx

Step 4

Substitute limits

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Answer

Next, we calculate the definite integral: (x3+2x24x+4)dx=14x4+23x32x2+4x\int (-x^3 + 2x^2 - 4x + 4) \, dx = -\frac{1}{4}x^4 + \frac{2}{3}x^3 - 2x^2 + 4x

Substituting the limits: =[14(1)4+23(1)32(1)2+4(1)][14(2)4+23(2)32(2)2+4(2)]= \left[-\frac{1}{4}(1)^4 + \frac{2}{3}(1)^3 - 2(1)^2 + 4(1)\right] - \left[-\frac{1}{4}(-2)^4 + \frac{2}{3}(-2)^3 - 2(-2)^2 + 4(-2)\right]

Step 5

Calculate shaded area

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Answer

Calculating these expressions:

For x=1x = 1: 14(1)+23(1)2(1)+4(1)=14+232+4=912+6122412=912-\frac{1}{4}(1) + \frac{2}{3}(1) - 2(1) + 4(1) = -\frac{1}{4} + \frac{2}{3} - 2 + 4 = \frac{9}{12} + \frac{6}{12} - \frac{24}{12} = \frac{-9}{12}

For x=2x = -2: 14(16)+23(8)2(4)8=41638=4+8163=123163=283-\frac{1}{4}(16) + \frac{2}{3}(-8) - 2(4) - 8 = -4 - \frac{16}{3} - 8 = -4 + 8 - \frac{16}{3} = -\frac{12}{3} - \frac{16}{3} = \frac{-28}{3}

Finally, the total area is: (912(283))=(912+11212)=10312\left( -\frac{9}{12} - (-\frac{28}{3}) \right) = (-\frac{9}{12} + \frac{112}{12}) = \frac{103}{12}

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