Linear equations are of degree 1. The degree of an equation is the largest SUM of the exponents on any term.
is linear because an equivalent form is:
And the largest exponent is 1, hence the degree of the equation is 1.
is NOT linear. Look at the equivalent form:
The degree of a term is the SUM of the exponents in that term, hence the term is of degree 2, therefore the equation is of degree 2, and therefore not linear.
Note that is equivalent to the above non-linear equation and is also non-linear.
Obviously, any equation that has higher powers is also non-linear. Included in the non-linear category are exponential, logarithmic, and
The standard form of a two-variable linear equation is:
Some texts require that A, B, and C be integers for proper standard form.