Rút gọn biểu thức :
1. \(\frac{x^6+2x^3y^3+y^6}{x^7-xy^6}\)
2.\(\frac{a^2+b^2-c^2+2ab}{a^2-b^2+c^2+2ac}\)
3.\(\frac{x^2+a^2-b^2-2bc+2ax-c^2}{x^2+b^2-a^2+2bx-2ac-c^2}\)
4. \(\frac{3x^3-2x^2+4x-5}{6x^2+3x-9}\)
5. \(\frac{3^{3x}-3^{3y}}{3^x+3^y}\)
Please, help me!~~~