This is Ana's Definition of the Derivative:
Observe that x3 + x = 30 when x = 3.
f(x) = x3 + 3
a = 3
Notice that f(3) = 3³ + 3 = 30, which confirms that equation of f(x) is correct.
f(x) = x³ + x
f '(x) =_______________________
f '(3) =__________
You just avoided a lot of Algebra!