01:39 – 因式分解 x^2 + bx + c | factorization of x^2 + bx + c05:11 – 例子 1 | example 106:20 – 因式分解 ax^2 + bx + c | factorization of ax^2 + bx + c11:54 – 例子 2 | example 213:52 – 因式分解 ax^2 + bxy + cy^2 | factorization of ax^2 + bxy + cy^2