Question 29773
As your question is stated ... it has two = signs.  I am going to assume that the =29 should actually be +29.

f(x) is just a fancy way of saying y.  When given a number such as f(2), it simply means that wherever that particular variable is, substitute in the given number.

f(2)
f(x) = -4x^2 + 3x + 29
f(2) = -4(2)^2 + 3(2) + 29
f(2) = -4(4) + 6 + 29
f(2) = -16 + 6 + 29
f(2) = -10 + 29
f(2) = 19