Slopes

1.) Using slopes, determine which of the set of three points lie on a straight line:

$\displaystyle (-1,-2),(6,-5),(-10,2)$

2.) The line segment drawn from $\displaystyle P(x,3)$ to $\displaystyle (4,1)$ is perpendicular to the segment drawn from $\displaystyle (-5,-6)$ to $\displaystyle (4,1)$. Find the value of x.

Thanks a bunch :)