Question

四边形ABCD为菱形,且A(a,1),B(3,5),C(7,3),D(b,-1),则实数a=?b=?

Answer 1

(a+7)/2=(3+b)/2;(7-a)²+（3-1）²=（b-3）²+(5+1）².a=1,b=5.