两道分解因式题,估计要用十字相乘法!1a^3-5a^2b-24ab^223ab^2-9a^2b^2+6a^3b^2还有一道：x^2-1/6x-1/6

Question

两道分解因式题,估计要用十字相乘法!
1 a^3-5a^2b-24ab^2
2 3ab^2-9a^2b^2+6a^3b^2
还有一道：x^2-1/6x-1/6

Answer 1

a^3-5a^2b-24ab^2
=a(a^2-5ab-24b^2)
=a(a+3b)(a-8b)
3ab^2-9a^2b^2+6a^3b^2
=3ab^2(1-3a+2a^2)
=3ab^2(1-2a)(1-a)
x^2-1/6x-1/6
=1/6(6x^2-x-1)
=1/6(2x-1)(3x+1)