Let there be the function [[$ f(x) = x^2 - x + 4 $]]. Calculate the value of the function at

a) [[$ x = 0 $]]

Answer: [[$ f(0) = $]]

b) [[$ x = 2 $]]

Answer: [[$ f(2) = $]]

c) [[$ x = -1 $]]

Answer: [[$ f(-1) = $]]

d) [[$ x = -2 $]]

Answer: [[$ f(-2) = $]]