bai 1: giai cac phuong trinh sau( bat dang thuc)
a/ $\sqrt{3x^{2} + 6x + 7} + \sqrt{5x^{2} + 10x + 14} = 4 - 2x - x^{2}$
b/ $x\sqrt{1 + x} + \sqrt{3 - x} = 2\sqrt{x^{2} + 1}$
c/ $\sqrt{5x - 5} + \sqrt{10x - 5} = \sqrt{15x - 10}$
d/ $\sqrt{x^{2} + x + 4} + \sqrt{x^{2} + x + 1} = \sqrt{2x^{2} + 2x + 9}$
e/ $\sqrt{x - 2} + \sqrt{4 - x}= x^{2} - 6x +11$
bai 2: xet su bien thien cua ham so $y = x^{3} + 12x + 9$ trên $(- \infty ; + \infty )$