# How do you find the slope of a line A(-10,0) B(0,-10)?

slope = (change in $y$) / (change in $x$)
That is: given two points $\left({x}_{0} , {y}_{0}\right)$ and $\left({x}_{1} , {y}_{1}\right)$ through which a line passes, the slope $m$ is given by the formula:
$m = \frac{\Delta y}{\Delta x} = \frac{{y}_{1} - {y}_{0}}{{x}_{1} - {x}_{0}}$
$m = \frac{- 10 - 0}{0 - \left(- 10\right)} = \frac{- 10}{10} = - 1$