Are all linear equations functions? Is there an instance in which a linear equation is not a function?

A linear equation which is a vertical line in NOT a function.

e.g. x = 5 is not a function, since for the given value of x=5, you can have more than one value of y.

Any other linear equation is a function.

Yes, all linear equations are functions except for one specific case. In mathematics, a function is a relation between a set of inputs (domain) and a set of outputs (range), where each input is uniquely mapped to exactly one output.

A linear equation represents a straight line on a coordinate plane and is defined by the form "y = mx + b", where "m" is the slope of the line, and "b" is the y-intercept. As long as the slope "m" is not equal to zero, the linear equation will represent a function because each input value (x-coordinate) determines a unique output value (y-coordinate).

However, when the slope "m" is equal to zero, the linear equation becomes "y = b" or a horizontal line parallel to the x-axis. In this case, every input value (x-coordinate) will have the same output value (y-coordinate), which means multiple inputs are mapped to a single output. Therefore, when the slope is zero, the linear equation is not a function.

To determine whether a linear equation is a function or not, you can examine the equation and check if the slope is zero. If the slope is zero, it is not a function. If the slope is any nonzero value, it is a function.