Let the units of the problem be miles and hours. The first plane's distance from point p can be described by
... x = 150 -450t
The second plane's distance from point p can be described by
... y = 200 -450t
Since their flight paths are at right angles, the Pythagorean theorem can be used to describe the distance between them (s).
... s² = x² + y²
... s² = (150 -450t)² + (200 -450t)² = 22500 -135000t +202500t² +40000 -180000t +202500t²
... s² = 40500t² -315000t +62500 = 2500(162t² -126t +25)
... s = 50√(162t² -126t +25)
