# What are the extrema of f(x) = 8 - 2x for x>=6?

$f \left(x\right)$ is a line with a negative slope, so on the interval $x \ge 6$, the maximum is at $x = 6$. There is no minimum because $f \left(x\right)$ is always decreasing, and the interval given is $\left[6 , \infty\right]$.