Uhm, the definition of a linear function is that f(a+b)=f(a)+f(b) and f(n·a)=n·f(a) (i.e. additivity and homogeneity). Maybe you are thinking by a first-degree

Uhm, the definition of a linear function is that f(a+b)=f(a)+f(b) and f(n·a)=n·f(a) (i.e. additivity and homogeneity). Maybe you are thinking by a first-degree polynomial, which is a straight line when graphed? http://en.wikipedia.org/wiki/Linear_function http://en.wikipedia.org/wiki/Linear_function