How do you know a function is decreasing or increasing at #x=1# given the function #4x^2-9x#?
Usually what people mean when they ask this question is "Is the slope of the tangent line at
Whether we think of the derivative as the slope of the tangent line or the rate of change, it is clear that when
This is generally explained by saying that,
(There is a bit of a conflict in terminology here. A function is constant at a single value of