Question 179816
Linear equations or linear functions are a subset of functions. 
Similarities are one unique output for each input and they are continuous by definition.
Yes, all linear equations are functions.
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Linear equations take the form
{{{y=mx+b}}}
There are many ways to make an equation non-linear. 
The simplest may be to change the power of the x exponent.
{{{y=mx^2+b}}}
or as an example,
{{{y=2x^2-1}}}
So if I put in x=1,
{{{y=2(1)-1=1}}}
and if I put in x=2,
{{{y=2(4)-1=7}}}
Here's a graph of that non-linear function. 
{{{ graph( 300, 300, -5, 5, -2, 8, 2x^2-1) }}}