1. A skydiver jumps from a moving aircraft when it is directly above a fixed point, O, on the ground.  The trajectory of the skydiver is then modelled by the function

      $h(x)=4900-{x}^{2}$

where $hm$ is the height of the skydiver above the ground and $x$ $m$ is the horizontal distance along the ground from point O.

(i) At what height does the skydiver jump from?

(ii) How far above the ground is the skydiver when their horizontal distance from $0$ is $50m$?

(iii) Explain why the model is not suitable for values of $x$ larger than $70m.$