We read your photo as:

Calculate the points of intersection of 2y = 8x − 2x2 and 2y = 2x. Make a neat sketch of the graphs and show the representative strip that you will use to calculate the area bounded by the two graphs.

Mathematics

ScanSolve AI Answer

Answer

64π3\frac{64\pi}{3}

Graph of y = x − 6

Use the left and right arrow keys to trace the curve, up and down to jump between key points, and plus and minus to zoom.

Key points of y = x − 6
Pointxy

Step-by-step solution

4 steps

To calculate the volume using the Shell Method about the x-axis, we need to integrate with respect to yy. The formula for the shell method rotating about the x-axis is V=∫cd2π∣y∣(xR−xL)dyV = \int_{c}^{d} 2\pi |y| (x_R - x_L) dy.

  1. Find the points of intersection of the two curves.

    The given equations are xy=−5xy = -5 and y=x−6y = x - 6.
    From the second equation, express xx in terms of yy: x=y+6x = y + 6.
    Substitute this into the first equation:

    (y+6)y=−5(y+6)y = -5 y2+6y=−5y^2 + 6y = -5 y2+6y+5=0y^2 + 6y + 5 = 0

    Factor the quadratic equation:

    (y+1)(y+5)=0(y+1)(y+5) = 0

    This gives y=−1y = -1 or y=−5y = -5.
    Now find the corresponding xx values:
    If y=−1y = -1, then x=−1+6=5x = -1 + 6 = 5. Intersection point: (5,−1)(5, -1).
    If y=−5y = -5, then x=−5+6=1x = -5 + 6 = 1. Intersection point: (1,−5)(1, -5).
    The limits of integration for yy are from c=−5c = -5 to d=−1d = -1.

  2. Express xx in terms of yy for both curves and identify xRx_R and xLx_L.

    From xy=−5xy = -5, we get x=−5yx = -\frac{5}{y}.
    From y=x−6y = x - 6, we get x=y+6x = y + 6.
    To determine which function is xRx_R (right) and xLx_L (left), pick a test value for yy between −5-5 and −1-1, for example y=−3y = -3:
    For x=−5yx = -\frac{5}{y}: x=−5−3=53≈1.67x = -\frac{5}{-3} = \frac{5}{3} \approx 1.67.
    For x=y+6x = y + 6: x=−3+6=3x = -3 + 6 = 3.
    Since 3>533 > \frac{5}{3}, the curve x=y+6x = y+6 is to the right (xRx_R) and x=−5yx = -\frac{5}{y} is to the left (xLx_L).
    So, xR=y+6x_R = y+6 and xL=−5yx_L = -\frac{5}{y}.

  3. Set up the integral for the volume using the Shell Method about the x-axis.

    Since the region is below the x-axis (where yy is negative), the radius of the cylindrical shell is ∣y∣=−y|y| = -y.

    V=∫−5−12π(−y)(xR−xL)dyV = \int_{-5}^{-1} 2\pi (-y) (x_R - x_L) dy V=∫−5−12π(−y)((y+6)−(−5y))dyV = \int_{-5}^{-1} 2\pi (-y) \left( (y+6) - \left(-\frac{5}{y}\right) \right) dy V=2π∫−5−1(−y)(y+6+5y)dyV = 2\pi \int_{-5}^{-1} (-y) \left( y+6 + \frac{5}{y} \right) dy V=2π∫−5−1(−y2−6y−5)dyV = 2\pi \int_{-5}^{-1} (-y^2 - 6y - 5) dy
  4. Evaluate the integral.

    V=2π[−y33−6y22−5y]−5−1V = 2\pi \left[ -\frac{y^3}{3} - \frac{6y^2}{2} - 5y \right]_{-5}^{-1} V=2π[−y33−3y2−5y]−5−1V = 2\pi \left[ -\frac{y^3}{3} - 3y^2 - 5y \right]_{-5}^{-1}

    Evaluate at the upper limit y=−1y = -1:

    (−(−1)33−3(−1)2−5(−1))=(−(−13)−3(1)+5)=13−3+5=13+2=73\left(-\frac{(-1)^3}{3} - 3(-1)^2 - 5(-1)\right) = \left(-\left(-\frac{1}{3}\right) - 3(1) + 5\right) = \frac{1}{3} - 3 + 5 = \frac{1}{3} + 2 = \frac{7}{3}

    Evaluate at the lower limit y=−5y = -5:

    (−(−5)33−3(−5)2−5(−5))=(−(−1253)−3(25)+25)=1253−75+25=1253−50=125−1503=−253\left(-\frac{(-5)^3}{3} - 3(-5)^2 - 5(-5)\right) = \left(-\left(-\frac{125}{3}\right) - 3(25) + 25\right) = \frac{125}{3} - 75 + 25 = \frac{125}{3} - 50 = \frac{125 - 150}{3} = -\frac{25}{3}

    Subtract the lower limit value from the upper limit value:

    V=2π(73−(−253))V = 2\pi \left( \frac{7}{3} - \left(-\frac{25}{3}\right) \right) V=2π(73+253)V = 2\pi \left( \frac{7}{3} + \frac{25}{3} \right) V=2π(323)V = 2\pi \left( \frac{32}{3} \right) V=64π3V = \frac{64\pi}{3}

    The volume generated is 64π3\frac{64\pi}{3}.

Was this helpful?

Try one yourself

A new problem that tests the same skill.

Still stuck on this one?

Ask a follow-up, and the answer starts from this question.

Got a different question?Ask your own question