# How do you find the linear approximation of a function?

The linear approximation $L \left(x\right)$ of a function is done using the tangent line to the graph of the function. The equation of the tangent line at $x = a$ is given by
$y = f ' \left(a\right) \left(x - a\right) + f \left(a\right)$,
$L \left(x\right) = f ' \left(a\right) \left(x - a\right) + f \left(a\right)$.