Why do this problem?
The problem gives practice in the usual techniques for cuve
sketching (considering symmetry, finding turning points, looking
for asymptotes). It also introduces the idea of a family of
curves.
Possible approach
Suggest different members of the class sketch the different graphs
(for a=1, 2 and 3). Have a class discussion about the results
they find.
Key question
Will the graphs have a similar shape for all values of a?
What about negative values of a?
Possible extension
If the class can differentiate simple functions defined
parametrically or implicitly then they could also try:
Squareness and
Folium of Descartes .
Show without recourse to any calculating aid that 7^{1/2} + 7^{1/3}
+ 7^{1/4} < 7 and 4^{1/2} + 4^{1/3} + 4^{1/4} > 4 . Sketch
the graph of f(x) = x^{1/2} + x^{1/3} + x^{1/4} -x