Let be a function such that f(-1)=1 . at each point on the graph of , the slope is given by dy/dx=x²-xy-y². which of the following statements is true?

a. f has a relative minimum at x = 1.
b. f has a relative maximum at x = 1.
c. f has neither a relative minimum nor a relative maximum at x = 1.
d. There is insufficient information to determine whether f has a relative minimum, maximum, or neither at x = 1.