Shape of a bridge is modeled by the equation y=-0.0044x^2+21.3, Find the length of the bridge?( All measurements are in meters).

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embizze | High School Teacher | (Level 1) Educator Emeritus

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We assign a coordinate system with ground level y=0, and assume the bridge is level.

The length of the bridge is the distance between the two x-intercepts. We set y=0 and solve for x:

`-0.0044x^2+21.3=0`

`-0.0044x^2=-21.3`

`x^2=4840.bar(09)`

`x~~+-69.6`

This is the distance from the axis of symmetry (the center of the bridge) to one side of the bridge, so the length of the bridge is approximately 2(69.6)=139.2m

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