Bias and variance tradeoff

This very nice post clearly explains the bias and variance tradeoff
http://www.learnopencv.com/bias-variance-tradeoff-in-machine-learning/

This tradeoff can be mathematically stated by the following equations

Another interesting post on the same topic can be found here
http://scott.fortmann-roe.com/docs/BiasVariance.html

The first aforementioned post nicely summarizes some of the main recommendations which Andrew NG gave in many of his talks
https://www.youtube.com/watch?v=F1ka6a13S9I