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First find the roots of the polynomial from the quadratic equation
-0.1875x2 + 0.5625x + 0.328125 = 0
It is EQUIVALENT to
x^2 - 3x - 1.75 = 0
The roots are
= = = .
= = -0.5; = = 3.5.
So, the arch is anchored at = -0.5 and = 3.5.
The stream is between x= 0 and x= 3,
The width of the stream is 3 - 0 = 3 meters.
The arch has maximum height exactly half the way between the roots at x= 1.5.
The height of the arch is the value of the polynomial at x= 1.5
= -0.1875*1.5^2 + 0.5625*1.5 + 0.328125 = 0.75 m.
Solved.