表达式4: "x" equals "f" left parenthesis, "y" , right parenthesisx=fy
4
表达式5: "f" Subscript, "i" "n" "v" , Baseline left parenthesis, "x" , right parenthesis equals signum left parenthesis, "f" left parenthesis, "b" , right parenthesis minus "f" left parenthesis, "a" , right parenthesis , right parenthesis Start integral from "a" to "b" , end integral, left brace, "x" greater than "f" left parenthesis, "y" , right parenthesis , 0 , right brace "d" "y" positive left brace, "f" left parenthesis, "b" , right parenthesis greater than "f" left parenthesis, "a" , right parenthesis : "a" , "b" , right bracefinvx=signfb−fa∫bax>fy,0dy+fb>fa:a,b
