Answer:
Linear functions are
[tex]y=2x-9\\y=-10.2\\3x+5y=15[/tex]
The only non-linear function is
[tex]y=3x^{2} +7[/tex]
Basically, a linear function is defined by those which curve is a line. Or their polynomial expression is first grade, that is, the major exponent of variables is one, which is not the case with the third function, that's why is not linear.
