PHÒNG GD&ĐT LANG CHÁNH TRƯỜNG THCS TÂN PHÚC BÀI THI KHẢO SÁT HSG LẦN 1 MÔN: TOÁN 8 Năm học: 2015 - 2016 Thời gian: 120 phút Họ và tên học sinh: .......................................................................................Lớp: ........ Trường THCS Tân Phúc ĐỀ BÀI: Bài 1: (4 điểm) Phân tích các đa thức sau thành nhân tử: (x + y + z) 3 – x3 – y3 – z3. b, x4 + 2010x2 + 2009x + 2010 Câu2. (4 điểm) Cho biểu thức: a. Rút gọn biểu thức A. b. Tính giá trị của A , Biết |x| =. c. Tìm giá trị của x để A < 0. d. Tìm các giá trị nguyên của x để A có giá trị nguyên. Bài 3: (3 điểm) Tìm giá trị nhỏ nhất của biểu thức . Bài 4 (3 điểm) Cho tam giác ABC vuông tại A có góc ABC bằng 600, phân giác BD. Gọi M,N,I theo thứ tự là trung điểm của BD, BC, CD. a, Tứ giác AMNI là hình gì? Chứng minh. b, Cho AB = 4cm. Tính các cạnh của tứ giác AMNI. Bài 5 (4 điểm) Hình thang ABCD (AB // CD) có hai đường chéo cắt nhau tại O. Đường thẳng qua O và song song với đáy AB cắt các cạnh bên AD, BC theo thứ tự ở M và N. a, Chứng minh rằng OM = ON. b, Chứng minh rằng c, Biết SAOB= 20082 (đơn vị diện tích); SCOD= 20092 (đơn vị diện tích). Tính SABCD. Câu 6 ( 2 điểm) Chứng minh rằng: BÀI LÀM: ...............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Tài liệu đính kèm: