document.write( "Question 406879: A parabolic arch has a span of 100 feet and a maximum height of 25 feet. Write an equation to represent the arch, then calculate the height of the arch 20 feet from the center \n" ); document.write( "

Algebra.Com's Answer #287147 by ewatrrr(24785) $\"\"$ $\"About$

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document.write( "Hi
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document.write( "A parabolic arch has a span of 100 feet and a maximum height of 25 feet. 
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document.write( "Using the vertex form of a parabola,  where(h,k) is the vertex
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document.write( "  y = a(x-50)^2 + 25  Vertex (50,25)
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document.write( "  0 = a50^2 + 25   |Using x-intercept Pt(0,0) to solve for a
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document.write( " -25/2500 = a
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document.write( "  y = (-1/100)(x-50)^2 + 25
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document.write( " height of the arch 20 feet from the center: 
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document.write( " x = 30
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document.write( " y = (-1/100)20^2 + 25
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document.write( " y = -4 + 25
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document.write( " y = 21ft
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