Question

ab + 4 + a + 4b factor

Answer 1

ab + 4 + a + 4b
FOIL... but reversed
( )( )
everything positive, so for now assume both brackets are plus
( + )( + )
AB so a x b
(a + )(b + )
you have a single a but u have 4b, so ur numbers are 4 and 1
also, 4b, so must be 4 x b, so 4 isnt in the same bracket as b
(a + 4)(b + 1)

so does this work out?
FOIL it and check

Answer 2

(a + 4)(b + 1)
FOIL
ab + 4b + 1a + 4 ... so yup