Find the rate of change in the function y = -3x

Rate of change = slope  = -3

 

 

 

or the derivative of -3x  is  -3

 

 

 

or take two points   say 2 and 4

               -3(2) = -6       -3(4) = -12           r.o.c = (-12 - - 6) /2 = - 3