本题目来源于试卷: IB MAI HL Functions Topic 2.2 Applications of Functions，类别为 IB数学
[问答题]
The security personnel at the entry of a rural caezyki *c*r4x3mpc2xduwwomi9+ u 0 elu8b -*u7kground activate a siren to alert campers when a wild animal is spotted nearby. The sound intensity, I, of the siren varies inversely with the square of the distance from the siren, d. When initially testing the siren, the security personnel found that at a dism+97w 0i2ox-lk uewuubud*c 8tance of 3 metres from the siren, the sound intensity is 5 watts per square metre ($Wm^{−2}$).
1.Show that I=$\frac{45}{d^2}$.
2.Sketch the curve of I for d>0, labelling the point (3,5).
The campers can only hear the siren if the sound intensity at their location is greater than $1.2\times10^{−5}Wm^{−2}$.
3.Find the minimum distance, in kilometers, from the siren where the campers can no longer hear the siren.
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