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^2+6}}}. 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/.4}}}
x^2 = 15
x = +{{{sqrt(15)}}} ~ +3.873
x = -{{{sqrt(15)}}} ~ -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