First, calculate the slope.


    The formula for the slope of a straight line passing through two given points (,)  and  (,)  is
        m = .

    Substitute the given data   = -2,   = -5,   = -9,  = -3  into the basic formula

        m =  =  = .


Next, find an equation of the line having the slope    and passing through the given point (-2,-6).


    An equation of a straight line in a coordinate plane which has the slope m and passes through the given point  P = (a,b)  is 

        y - b = m*(x-a).     

    Substitute here  m = ,  a = -2,  b = -6,  and you will get

        y - (-6) = ,  or equivalently

        y + 6    = .

    It is the equation in the slope-point form.


    Having this equation, you may transform it to any other equivalent form.