SOLUTION: A tunnel is constructed using cut and cover construction with the cross section represented by the following equation of a parabola {{{y=-0.4x^2+6}}}. Calculate the width of the tu

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Question 176589: A tunnel is constructed using cut and cover construction with the cross section represented by the following equation of a parabola y=-0.4x%5E2%2B6. Calculate the width of the tunnel by solving the quadratic equation using another method than graphs.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A tunnel is constructed using cut and cover construction with the cross section represented by the following equation of a parabola y=-0.4x%5E2%2B6. Calculate the width of the tunnel by solving the quadratic equation using another method than graphs
:
find the x intercepts
-.4x^2 + 6 = 0
-.4x^2 = -6
Multiply eq by -1
.4x^2 = +6
x^2 = 6%2F.4
x^2 = 15
x = +sqrt%2815%29 ~ +3.873
x = -sqrt%2815%29 ~ -3.873
:
The width of the tunnel will be the distance between these two values
3.873 - (-3.873) =
3.873 + 3.873 = 7.746