An example of an equation that is not a linear function is \( y = x^2 \).
This is not a linear function because it does not represent a straight line when graphed. Instead, it creates a parabola that opens upwards, demonstrating a quadratic relationship between \( x \) and \( y \). Linear functions have the form \( y = mx + b \), where \( m \) and \( b \) are constants, resulting in a constant rate of change; but in the case of \( y = x^2 \), the rate of change varies depending on the value of \( x \).