Question: what is the slope of the tangent line to the curve?
Answer: The slope of a curve y = f(x) at the point P means the slope of the tangent at the point P. We need to find this slope to solve many applications since it tells us the rate of change at a particular instant. [We write y = f(x) on the curve since y is a function of x. That is, as x varies, y varies also.]