中二簡單factorization

1. y^3 + y^2 + y + 1
= (y^3 + y^2) + (y + 1)
= y^2(y + 1) + (y + 1)
= (y + 1)(y^2 + 1)
2. 9x^3 - 5x^2 - 18x + 10
= (9x^3 - 5x^2) - (18x - 10)
= x^2(9x - 5) - 2(9x - 5)
= (9x - 5)(x^2 - 2)
3. 2 + 3a - 14a^2 - 21a^3
= (2 + 3a) - (14a^2 + 21a^3)
= (2 + 3a) - 7a^2(2 + 3a)
= (2 + 3a)(1 - 7a^2)
4. 4b^2 - 6b^3 - 2 + 3b
= (4b^2 - 6b^3) - (2 - 3b)
= 2b^2(2 - 3b) - (2 - 3b)
= (2 - 3b)(2b^2 - 1)