AP Calculus AB · Topic 7.3

Slope Fields Practice

Part of Differential Equations.(FUN-7.C)

Practice questions

14

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Sample questions

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  1. Sample 1difficulty 2/5

    For dy/dx=xydy/dx = x - y, where on the plane is the slope <strong>zero</strong>?

    • A

      y=xy = x

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    • B

      y=0y = 0

    • C

      y=xy = -x

    • D

      x=0x = 0

    Why

    xy=0y=xx - y = 0 \Rightarrow y = x. Slopes are zero along this line.

  2. Sample 2difficulty 2/5

    The slope field has constant positive slope at every point. Which differential equation does it correspond to?

    • A

      dy/dx=0dy/dx = 0

    • B

      dy/dx=xdy/dx = x

    • C

      dy/dx=ydy/dx = y

    • D

      dy/dx=1dy/dx = 1

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    Why

    Constant slope at all points → dy/dx=dy/dx = constant.

  3. Sample 3difficulty 2/5

    A slope field has slope 11 everywhere on the line y=xy = x and slope 00 on y=0y = 0. The DE is likely

    • A

      dy/dx=xdy/dx = x

    • B

      dy/dx=xydy/dx = x y

    • C

      dy/dx=ydy/dx = y

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    • D

      dy/dx=yx+1dy/dx = y - x + 1

    Why

    dy/dx=ydy/dx = y: on y=xy = x, slope = xx (not constant 1)... checking dy/dx=ydy/dx = y: at y=0y = 0, slope is 00 ✓. At y=1y = 1, slope is 11. Best fit among options.

  4. Sample 4difficulty 2/5

    A slope field shows the <strong>direction</strong> but not the speed of motion along solution curves. The slope-field segments at each point encode

    • A

      Curvature

    • B

      The value of f(x,y)f(x, y) in dy/dx=f(x,y)dy/dx = f(x, y)

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    • C

      yy

    • D

      xx

    Why

    Slope field plots yy' at each grid point.

  5. Sample 5difficulty 3/5

    Multiple solution curves of a slope-field DE

    • A

      Must coincide

    • B

      Are perpendicular to segments

    • C

      Are always horizontal

    • D

      Are tangent to slope-field segments at each point

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    Why

    Each solution curve at (x,y)(x, y) has slope equal to the field direction.