# linear

The graph of *y* = *ax* + *b*.

To be linear implies having only a multiplicative factor. A **linear relationship** is a relationship between two variables such that, if one is plotted as
a function of the other (see analytical
geometry), the result is a straight line.
If *f*( *x*) is a **linear function**, then *f* (*a*+*b*)
= *f* (*a*) + *f* (*b*) and *c* * f *(*x*)
= *f *(*cx*) must both be true for all values of *a*, *b*, *c*, and *x*.