what can I do to find the factors of two numbers, easely ans fast?

Question

some mental method you can do to find it ASAP

example, find the factors of 8 and 9
(which two numbers can be added, give you 9, and multiplied give you 8? just an example)

Answer 1

unfortunately your question does not make a lot of sense...
but if you want to find two numbers n and m, such that
n+m =9 and
nm=8
then you need to solve this system of 2 equations:
n= 9-m
so
(9-m)m=8
9m -m^2 -8=0
or
m^2 -9m +8 =0
(m-8)(m-1)=0
therefore m=8 and n=1
or m=1 and n =8.