Is there a value of x for which these equal? Call that value and try to find it.
This is interesting. It means that for a second-degree function — a parabola — the slope of the secant line between two points equals the instantaneous slope (that is, the slope of the tangent line) of the function halfway through the interval.
f(b); tangent and secant lines slope downward” width=”220″ height=”274″ />