Two trees 20 metres and 30 metres long, lean across a passageway
between two vertical walls. They cross at a point 8 metres above
the ground. What is the distance between the foot of the trees?
The equation a^x + b^x = 1 can be solved algebraically in
special cases but in general it can only be solved by numerical
methods. In this short problem, try to find the location of the
roots of some unusual functions by finding where they change
sign.