# What is the formula for the slope of a secant line?

$\frac{\Delta y}{\Delta x} = \frac{{y}_{2} - {y}_{1}}{{x}_{2} - {x}_{1}} = \frac{f \left(x + \Delta x\right) - f \left(x\right)}{\Delta x} = \frac{f \left(b\right) - f \left(a\right)}{b - a}$