The range of an ambulance service is a circular region bounded by the equation x^2 + y^2 = 400. A straight road within the service area is represented by y = 3x + 20. Find the length of the road that lies within the range of the ambulance service (round your answer to the nearest hundredth). Recall that the distance formula is [tex]d=\sqrt{x(x2-x1)^2+(y2-y1)^2[/tex]

Respuesta :

The straight road crosses the boundaries of the range of the ambulance service at two points

The length of the road that lies within the range of the ambulance service is approximately 37.95

Reason:

The function that represents the ambulance circular service area is x² + y² = 400

The equation that represents the straight road,  y = 3·x + 20

Required:

Length of the road that lies within the range of he ambulance

Solution:

The length of the road is given by the distance between the intersection

points of the road and the ambulance service region as follows;

At the intercepts, we have;

The x, and y-values of the line and the circle are equal, therefore, we have;

At the intercept, y = 3·x + 20, which gives;

x² + y² = 400

x² + (3·x + 20)² = 400

x² + 9·x² + 120·x + 400 = 400

10·x² + 120·x + 400 - 400 = 0

10·x² + 120·x = 0

x² + 12·x = 0

x² + 12·x = x·(x + 12) = 0

  • x = 0, or -12

When x = 0, y = 3×0 + 20 = 20

When x = -12, y = 3×(-12) + 20 = -16

The intersection points of the line and the circle are;

  • A(0, 20), and B(-12, -16)

The length of the segment AB, d, is given as follows;

  • d = [tex]\sqrt{((-12) - 0)^2 + (-16 - 20)^2} = \sqrt{1440} =12 \cdot \sqrt{10}[/tex]

The length of the road that lies within the range of the ambulance service, d, given to the nearest hundredth = 12·√(10) ≈ 37.95

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