Here's the question you clicked on:
MarcLeclair
Graph the function f(x) = x + 4 / x Graph the secant line that passes through the points (1,5) and (8,8.5) on the same set of axes Find the number c that satisfies the conclusion of the Mean Value Theorem for f on [1,8]
So do I have to find the second derivative, and critical points? then sketch it, THEN find the line? or i can just use f'(c) = f(a)-f(b)/a-b ?
Some hints from algebra would be that there is a vertical asymptote at x=0 and a slant asymptote at y=x. A first derivative test will then tell you the extrema. At that point a second derivative test will just confirm what should be obvious at that point, so I would just graph it without the second derivative. You can draw the secant line by simply drawing a line through the given points on the graph. They didn't ask for the line's equation, so I wouldn't look for it. Then use your Mean Value Theorem as you stated to find the x location of the tangent line whose slope matches the slope of the secant line. They didn't ask, but if you draw a line on the graph of the function with that slope at the x location that you find, you should have two parallel lines on your graph.