1 thuc hien phep tinh
a) 2x^2(3x^2+2x-3)
b) (x-2) (x+2)+x(1-x)
2 phan tich da thuc ra nhan tu
a) 2x^2-4x
b) 2x(x-y)+3(x-y)
c) x^2+2x+1-y^2
3 tim x
a) (2x+1)(x+1) -2x^2 =0
b) 15x^2-5x=0
4 cho hinh binh hanh ABCD, AC giao BD tai O. Goi M,N la giao diem cua OB va OD. C/m tu giac AMCNla hinh binh hanh . Tia AM cat BC tai E, tia CN cat AD tai F. C/m AC, BD, EF dong quy