find coordinate on line at given distance from given coordinate I got two coordinates of a straight line $(-2,-4)$ and $(3,4)$. How can i find a coordinate that lies on this line and is $5$ units away from the $(-2,-4)$ coordinate?

We define vector from first point to second: 
$ \vec{w} = [3,4]-[-2,-4] = [5,8] $
Module of this vector is:
$|w| = \sqrt{5^2+8^2} \approx 9,434  $
Hence a the unit vector in this direction has value:
$ \vec{u} := \vec{w} / |\vec{w}| = [5/|\vec{w}|, 8/|\vec{w}| ] = [0.53,  0.85] $
And distance from $(-2,-4)$ is:
$(-2,-4) + 5\vec{u} = (-2,-4) + [2.65, 4.25] = (0.65, 0.25) $
or in the reverse direction:
$(-2,-4) - 5\vec{u} = (-2,-4) - [2.65, 4.25] = ( -4.65, -8.25) $.
