That sounds like something taken from the book: Burn Math Class. There is always f(b) > f(a) <=> f increases in [a, b] or f(b) /= f(a) <=> f changes in [a,b].

That sounds like something taken from the book: Burn Math Class. There is always f(b) > f(a) <=> f increases in [a, b] or f(b) /= f(a) <=> f changes in [a,b]. But how useful is that?