



 
Hello. You can find the width of the arch if you can find the x values where the parabola crosses the horizontal axis. What is the value of y at both of these points? It is zero. So we can replace y with 0 in your equation:
Now if you solve for x, you will get two values of x which correspond to the two locations on the graph. What is the distance between these points? That's the width w. Hope this helps,  


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