Find and write in simplest form:

題目：

Find and write in simplest form:
Given f(x) = x² :
(a) f(f(b))
(b) [f(x)-f(a)]/(x-a)
(c) [f(x+h)-f(x)]/h

解答：

(a) f(f(b))
=f(b^2)
=b^4
(b) [f(x)-f(a)]/(x-a)
=[x^2-a^2]/(x-a)
=x+a
(c) [f(x+h)-f(x)]/h
=[(x+h)^2-x^2]/h
=(2xh+h^2)/h
=2x+h