Derivative of k times a function is k times derivative of the function. Thus[br] [math]\frac{d}{dx}\left(kf\left(x\right)\right)=k\frac{d}{dx}\left(f\left(x\right)\right)[/math][br]Sum/Difference of the derivative of two functions is sum/difference of the derivatives of the two functions. Thus [br] [math]\frac{d}{dx}\left(f\left(x\right)\pm g\left(x\right)\right)=\frac{d}{dx}\left(f\left(x\right)\right)\pm\frac{d}{dx}\left(g\left(x\right)\right)[/math][br][br]These two rules show that the process of finding derivatives is linear. Namely,[br][br] [math]\frac{d}{dx}\left(kf\left(x\right)+lg\left(x\right)\right)=k\frac{d}{dx}\left(f\left(x\right)\right)+l\frac{d}{dx}\left(g\left(x\right)\right)[/math][br][br]The purpose of this applet is to facilitate practice of this rule.