2. In each case, find the critical numbers of f(r). Then use the second derivative test

to decide whether the critical numbers lead to relative extrema. If f"(c) = 0 or

f"(c) does not exist for a critical number c; then the second derivative test gives no

information. In this case, use an alternative method instead (for example the first

derivative test).

(a) f(x) = x³ - 6x² +7

(b) f(x) = x^7/3 + x^4/3