Tài liệu toán cấp 3

http://toan.hoctainha.vn/Thu-Vien/Chuyen-De/113562/cac-dang-bai-tap-viet-phuong-trinh-mat-phang-trong-khong-gian

http://baitaptoan.net/viet-phuong-trinh-mat-phang/

http://toanhocviet.com/phuong-trinh-duong-thang_n59398_g792.aspx