運算式 4: "y" equals "g" left parenthesis, "a" , right parenthesis left parenthesis, "x" minus "a" , right parenthesis plus "f" left parenthesis, "a" , right parenthesisy=gax−a+fa
4
運算式 5: left parenthesis, "a" , "f" left parenthesis, "a" , right parenthesis , right parenthesisa,fa
