Factorise the following, with steps

Step-by-step explanation:

1) Sum = - 9

Product = -36

Factors = -12 , 3     {-12 + 3 = -9  & -12*3 = -36}

3a²  - 9a - 12 = 3a² + 3a - 12a - 12

                    =3a(a + 1) - 12(a + 1)

                    = (a + 1) (3a - 12)

2) 4a² + 38a - 20 = 4a² + 40a - 2a  - 20

                            =4a(a + 10) - 2(a + 10)

                            =(a + 10)(4a - 2)

3) 11a² + 30a - 9 = 11a² + 33a - 3a - 9

                          = 11a(a + 3) - 3(a + 3)

                          =(a + 3)(11a - 3)

after simplifying it i got: -36.25 as my answer. hope that !