To answer this problem, you have to have a good foundation in factoring polynomial expressions. It has to be taken into account the knowledge in division and fractions.
The expression
(y+7)^2 - 100
can be factored as
[ (y+7) + 10 ] [ (y+7) - 10 ]
Further simplifying the expressions
[ y + 7 + 10 ] [ y + 7 - 10 ]
( y + 17 ) ( y - 3)
So the product of two linear binomials is
(y+17)(y-3)