ADDITION AND SUBTRACTION OF POLYNOMINALS

step 1.  Get rid of parentheses and simplify the expression.
         Examples:
         (1)  A(B+C) =  AB+AC
         (2)  A(B-C) =  AB-AC
         (3)  (4A+5B)+(7AB+3BC)
              4A+5B+7AB+3BC    (GET RIDE OF PARENTHESE)
         (4)  2(2A+2B)+3(3A-3B)
              4A+4B   +9A-9B   (GET RIDE OF PARENTHESE)
              13A-5B           (SIMPLIFY)
         (5)  2(2A+2B)-3(3A-3B)
              4A+4B   -9A+9B   (GET RIDE OF PARENTHESE)
              -5A+13B          (SIMPLIFY)
REMEMBER: a - times a - = a +.
          a + times a - = a -.