Slope = ( 5 - - 11) /( -4 - 1) = 16 / -5 = -16/5
Equation
y = (-16/5)(x -1) - 11 multiply through by 5
5y = -16( x - 1) - 55
5y = -16x + 16 - 55
5y = - 16x - 39 divide through by -39 and rearange as
(-5/39)y - ( 16/39)x = 1
x / ( -39/16) + y / ( -39/5 ) = 1
a = -39/16