Which statement best describes how to determine whether f(x) = x² - x + 8 is an even function?
a. Determine whether -x² - (-x) + 8 is equivalent to x² - x + 8.
b. Determine whether (-x)² - (-x) + 8 is equivalent to x² - x + 8.
c. Determine whether -x² - (-x) + 8 is equivalent to -x² - x + 8.
d. Determine whether (-x)² - (-x) + 8 is equivalent to -x² - x + 8.