document.write( "Question 1150069: An arch is in the shape of a parabola. It has a span of 180 meters and a maximum height of 15 meters. What is the equation of the parabola?\r
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Algebra.Com's Answer #771428 by ikleyn(52834) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "Place the origin of the coordinate system on the ground level under at the vertex of the parabola, \r\n" );
document.write( "i.e. under the top point of the arc.\r\n" );
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document.write( "Let x be horizontal axis and y be the vertical axis, directed up.\r\n" );
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document.write( "Then the equation of the parabola is  y = -ax^2 + 15.\r\n" );
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document.write( "Then the span of the parabola is from x = -90 m to x= 90 m.\r\n" );
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document.write( "Hence,  y = 0 = ,   or\r\n" );
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document.write( "    a*90^2 = 15,\r\n" );
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document.write( "    a =  =  =  = .\r\n" );
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document.write( "Thus the equation of the parabola is  y = .   ANSWER\r\n" );
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