I am reading the proof for the M.V.T, mostly understanding it all, except for this one step. Here is the link to it: http://tutorial.math.lamar.edu/Classes/CalcI/DerivativeAppsProofs.aspx#Extras_DerAppPf_MVT(adsbygoogle = window.adsbygoogle || []).push({});

It's near the bottom of the page.

What I don't precisely is why they create a new function, g(x), which is defined as f(x) subtracted by the equation for the secant line. A few steps after this they are able to redefine the interval (a, b) for this new function g(x), where the endpoints are equal to equal to each other, but I just don't understand the motive for this. What does it accomplish in proving this theorem?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Mean Value Theorem Proof

**Physics Forums | Science Articles, Homework Help, Discussion**