If f prime is negative, if it's less than zero, then the function itself is decreasing. The slope of the tangent line will be negative. You could, f prime could be positive while decreasing. For example, f prime could be doing something like this. And even though f prime would be decreasing in this situation, the actual value of the derivative would be positive, which means the function would be increasing in that scenario. So I would rule this one out. For values of x larger than three, as x values increase, the values of f of x decrease.