表达式3: 0 less than "y" less than "f" left parenthesis, "c" "x" , right parenthesis left brace, 0 less than "x" less than StartFraction, 1 Over "c" , EndFraction , right brace0<y<fcx0<x<1c
3
表达式4: "f" left parenthesis, "c" "x" , right parenthesis left brace, 0 less than "x" less than StartFraction, 1 Over "c" , EndFraction , right bracefcx0<x<1c
4
表达式5: "f" left parenthesis, "c" "x" , right parenthesisfcx