1. A(1,-4-2) B(3,1,2),C(5,2,-1)> K la chan duong phan giac ha tu A cua tam giac ABC , viet phuong trinh mat phang qua K va vuong goc AB ( ko dc su dung cach viet phuong trinh duong thang )
2. A(1,1,2) B(-1,0,4) C(3,2,-1), D(5,4,-3) . Tinh khoang cach tu mat cau noi tiep den tu dien ABCD??