## swiftskier96 15. You live near a bridge that goes over a river. The underside of the bridge is an arch that can be modeled with the function y = –0.000471x² + .837x where x and y are measured in feet. How high above the river is the bridge (the top of the arch)? How long is the section of bridge above the arch? (1 point) The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 1,777.07 ft. The bridge is about 371.85 ft. above the one year ago one year ago

1. swiftskier96

15. You live near a bridge that goes over a river. The underside of the bridge is an arch that can be modeled with the function y = –0.000471x² + .837x where x and y are measured in feet. How high above the river is the bridge (the top of the arch)? How long is the section of bridge above the arch? (1 point) The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 1,777.07 ft. The bridge is about 371.85 ft. above the river, and the length of the bridge above the arch is about 888.54 ft. The bridge is about 1,777.07 ft. above the river, and the length of the bridge above the arch is about 371.85 ft.

2. swiftskier96

@Frostbite

3. Frostbite

2 sec

4. Frostbite

Swiftskier you can do differentiation right?

5. swiftskier96

I remember learning it, but i dont remember how to do it.

6. Frostbite

Alright because if I understand the question right (maybe, maybe not) we can do the following: $\frac{ dy }{ dx }=\left( -4.7*10^{-4} x ^{2}+0.837x\right)^{'}=0.837-9.42*10^{-4}x$ We check for horizontal tangent: $\frac{ dy }{ dx }=0$ $0.837-9.42*10^{-4}x=0$ $x=888.535$ Then you can check for y your self, think it is right? or have I misunderstood the question?

7. Frostbite

ment -4.71 in the first equation sorry.

8. swiftskier96

Well it shortens it because now i know its either A or C.

9. Frostbite

you check for A or C by insetting the x value inside the original equation

10. swiftskier96

Ok ill try that.

11. Frostbite

I get the following result, but please make a check your self. $-4.71*10^{-4}*888.535^{2}+0.837*888.535=371.852$

12. Frostbite

and see if you agree

13. swiftskier96

Yeah i got the same. So its C then. :) Thanks for all the help!!!!!

14. Frostbite

No problem :)