Solved on Feb 22, 2024

Find the area between the cubic curves y=x313x2+30xy=x^{3}-13x^{2}+30x and y=x3+13x230xy=-x^{3}+13x^{2}-30x.

STEP 1

Assumptions
1. We are given two functions: y=x313x2+30xy = x^3 - 13x^2 + 30x and y=x3+13x230xy = -x^3 + 13x^2 - 30x.
2. We need to find the area between these two curves.
3. The area between the curves is the integral of the upper function minus the integral of the lower function between the points of intersection.

STEP 2

First, we need to find the points of intersection between the two curves. This is where the two functions are equal to each other.
x313x2+30x=x3+13x230xx^3 - 13x^2 + 30x = -x^3 + 13x^2 - 30x

STEP 3

Simplify the equation by moving all terms to one side.
2x326x2+60x=02x^3 - 26x^2 + 60x = 0

STEP 4

Factor out the common term xx.
x(2x226x+60)=0x(2x^2 - 26x + 60) = 0

STEP 5

Solve for xx by setting each factor equal to zero.
x=0or2x226x+60=0x = 0 \quad \text{or} \quad 2x^2 - 26x + 60 = 0

STEP 6

Factor the quadratic equation or use the quadratic formula to find the roots.
2x226x+60=(2x10)(x6)=02x^2 - 26x + 60 = (2x - 10)(x - 6) = 0

STEP 7

Solve for xx.
x=5orx=6x = 5 \quad \text{or} \quad x = 6

STEP 8

Now we have the points of intersection: x=0x = 0, x=5x = 5, and x=6x = 6.

STEP 9

To find the area between the curves, we need to integrate the difference between the two functions from x=0x = 0 to x=5x = 5 and from x=5x = 5 to x=6x = 6.

STEP 10

Set up the integral for the area from x=0x = 0 to x=5x = 5.
Area1=05[(x3+13x230x)(x313x2+30x)]dxArea_{1} = \int_{0}^{5} [(-x^3 + 13x^2 - 30x) - (x^3 - 13x^2 + 30x)] \, dx

STEP 11

Simplify the integrand by combining like terms.
Area1=05[2x3+26x260x]dxArea_{1} = \int_{0}^{5} [-2x^3 + 26x^2 - 60x] \, dx

STEP 12

Integrate the function with respect to xx.
Area1=[12x4+263x330x2]05Area_{1} = \left[ -\frac{1}{2}x^4 + \frac{26}{3}x^3 - 30x^2 \right]_{0}^{5}

STEP 13

Evaluate the integral at the bounds x=0x = 0 and x=5x = 5.
Area1=(12(5)4+263(5)330(5)2)(12(0)4+263(0)330(0)2)Area_{1} = \left( -\frac{1}{2}(5)^4 + \frac{26}{3}(5)^3 - 30(5)^2 \right) - \left( -\frac{1}{2}(0)^4 + \frac{26}{3}(0)^3 - 30(0)^2 \right)

STEP 14

Calculate the value of the integral from x=0x = 0 to x=5x = 5.
Area1=(12(625)+263(125)30(25))(0)Area_{1} = \left( -\frac{1}{2}(625) + \frac{26}{3}(125) - 30(25) \right) - (0)
Area1=(312.5+32503750)Area_{1} = \left( -312.5 + \frac{3250}{3} - 750 \right)
Area1=(312.5+1083.33750)Area_{1} = \left( -312.5 + 1083.33 - 750 \right)
Area1=20.83Area_{1} = 20.83

STEP 15

Set up the integral for the area from x=5x = 5 to x=6x = 6.
Area2=56[(x313x2+30x)(x3+13x230x)]dxArea_{2} = \int_{5}^{6} [(x^3 - 13x^2 + 30x) - (-x^3 + 13x^2 - 30x)] \, dx

STEP 16

Simplify the integrand by combining like terms.
Area2=56[2x326x2+60x]dxArea_{2} = \int_{5}^{6} [2x^3 - 26x^2 + 60x] \, dx

STEP 17

Integrate the function with respect to xx.
Area2=[12x4263x3+30x2]56Area_{2} = \left[ \frac{1}{2}x^4 - \frac{26}{3}x^3 + 30x^2 \right]_{5}^{6}

STEP 18

Evaluate the integral at the bounds x=5x = 5 and x=6x = 6.
Area2=(12(6)4263(6)3+30(6)2)(12(5)4263(5)3+30(5)2)Area_{2} = \left( \frac{1}{2}(6)^4 - \frac{26}{3}(6)^3 + 30(6)^2 \right) - \left( \frac{1}{2}(5)^4 - \frac{26}{3}(5)^3 + 30(5)^2 \right)

STEP 19

Calculate the value of the integral from x=5x = 5 to x=6x = 6.
Area2=(12(1296)263(216)+30(36))(12(625)263(125)+30(25))Area_{2} = \left( \frac{1}{2}(1296) - \frac{26}{3}(216) + 30(36) \right) - \left( \frac{1}{2}(625) - \frac{26}{3}(125) + 30(25) \right)
Area2=(64856163+1080)(312.532503+750)Area_{2} = \left( 648 - \frac{5616}{3} + 1080 \right) - \left( 312.5 - \frac{3250}{3} + 750 \right)
Area2=(6481872+1080)(312.51083.33+750)Area_{2} = \left( 648 - 1872 + 1080 \right) - \left( 312.5 - 1083.33 + 750 \right)
Area2=144+20.83Area_{2} = -144 + 20.83
Area2=123.17Area_{2} = -123.17

STEP 20

Since area cannot be negative, we take the absolute value of Area2Area_{2}.
Area2=123.17=123.17Area_{2} = | -123.17 | = 123.17

STEP 21

Add the two areas to find the total area between the curves.
TotalArea=Area1+Area2Total\, Area = Area_{1} + Area_{2}
TotalArea=20.83+123.17Total\, Area = 20.83 + 123.17

STEP 22

Calculate the total area.
TotalArea=144Total\, Area = 144
The area between the curves is 144 square units.

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