w^3      <-- the 1st term, its coefficient is 1, it is the same as 1w^3
-4w^2    <-- the 2nd term, its coefficient is -4.
-7w      <-- the 3rd term, its coefficient is -7.
+9       <-- the 4th term, its coefficient is +9.  A number with no letter
             multiplied by it is considered as its own coefficient, because
             it could be considered as +9w^0

Edwin