# How do you write the equation in point slope form given (4,1) , m=undefined?

$y - 1 = \frac{4 - c}{1 - d} \left(x - 4\right)$
make another point $\left(c , d\right)$
$m = \frac{4 - c}{1 - d}$
$y - 1 = \frac{4 - c}{1 - d} \left(x - 4\right)$