# 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*.