Step-by-step explanation:
multiply the first bracket with the second
and get -a squared -4a+3a+12
then we group like and unlike terms
so -4a+3a = -a
our new equation will be -a (squared)-a+12=0
we equals to zero to remove negative signs and it will be
a squared +a-12
then we find the factors.
And our factors are 3a-4a
=a squared +3a-4a-12=0
We factorise and answer will be
(a+3) (a-4)=0
so a = -3 or 4
