Question 132018
1.  Pick two points, any two because the answer to both your other questions is no.  Call one of them {{{P[1]}}} and the other {{{P[2]}}}, again, it doesn't matter which.


The x- and y-coordinates of {{{P[1]}}} are {{{x[1]}}} and {{{y[1]}}}.  Likewise, the x- and y-coordinates of {{{P[2]}}} are {{{x[2]}}} and {{{y[2]}}}.


The formula for the slope of a line given two points is {{{((y[1]-y[2])/(x[1]-x[2]))}}}.


All you need to to is put the coordinate values from the points you selected into the formula and do the arithmetic.


Example:  Let's say you chose the points P1(2,4) and P2(1,3), then:


{{{cartoon(((y[1]-y[2])/(x[1]-x[2])),((red(4)-y[2])/(x[1]-x[2])),((4-red(3))/(x[1]-x[2])),((4-3)/(red(2)-x[2])),((4-3)/(2-red(1))))}}}




{{{(4-3)/(2-1)=1/1=1}}}, and the slope is 1.