表达式3: 1 "f" Subscript, "h" "e" "a" "r" "t" 2 , Baseline left parenthesis, "x" , "y" , right parenthesis equals 0 left brace, StartAbsoluteValue, "x" , EndAbsoluteValue less than or equal to 1.5 , right brace left brace, StartAbsoluteValue, "y" , EndAbsoluteValue less than or equal to 1.5 , right brace1fheart2x,y=0x≤1.5y≤1.5
3
表达式4: 1 "f" Subscript, "h" "e" "a" "r" "t" 2 , Baseline left parenthesis, "x" , "y" , right parenthesis equals 01fheart2x,y=0
