表达式13: negative StartFraction, left parenthesis, "a" minus "c" , right parenthesis Over left parenthesis, "b" minus "d" , right parenthesis , EndFraction left parenthesis, "x" minus StartFraction, left parenthesis, "a" plus "c" , right parenthesis Over 2 , EndFraction , right parenthesis plus StartFraction, left parenthesis, "b" plus "d" , right parenthesis Over 2 , EndFraction−a−cb−dx−a+c2+b+d2
13
表达式14: negative StartFraction, left parenthesis, "a" minus "f" , right parenthesis Over left parenthesis, "b" minus "g" , right parenthesis , EndFraction left parenthesis, "x" minus StartFraction, left parenthesis, "a" plus "f" , right parenthesis Over 2 , EndFraction , right parenthesis plus StartFraction, left parenthesis, "b" plus "g" , right parenthesis Over 2 , EndFraction−a−fb−gx−a+f2+b+g2
14
表达式15: negative StartFraction, left parenthesis, "c" minus "f" , right parenthesis Over left parenthesis, "d" minus "g" , right parenthesis , EndFraction left parenthesis, "x" minus StartFraction, left parenthesis, "c" plus "f" , right parenthesis Over 2 , EndFraction , right parenthesis plus StartFraction, left parenthesis, "d" plus "g" , right parenthesis Over 2 , EndFraction−c−fd−gx−c+f2+d+g2
