Consider the function f(x) = x². Describe the image set and determine whether the function is one-to-one and whether it is onto if:
(a) Domain (D) = Real numbers (R), Range (R) = Real numbers (R).
(b) Domain (D) = Real numbers (R), Range (R) = Non-negative real numbers (R+).
(c) Domain (D) = Non-negative real numbers (R+), Range (R) = Real numbers (R).
(d) Domain (D) = Non-negative real numbers (R+), Range (R) = Non-negative real numbers (R+).