If you didn't already know, we can use the "F.O.I.L" method.
"F.O.I.L" stands for:
color(red)"F": First, as in you multiply the first two terms in each ()
color(blue)"O": Outer (multiply the outer terms)
color(green)"I": Inner (multiply the inner terms)
color(orange)"L": Last (multiply the last terms
(color(red)(2y)+11)(color(red)(2y)-11) : color(red)(4y^2)
(color(blue)(2y)+11)(2ycolor(blue)(-11)) : color(blue)(-22y)
(2y+color(green)(11))(color(green)(2y)-11) : color(green)(22y)
(2y+color(orange)(11))(2ycolor(orange)(-11)) : color(orange)(-121)
Gathering this information, we can rewrite the expression and combine like terms:
4y^2color(red)(-22y+22y)-121
4y^2cancel(color(red)(-22y+22y))-121
The middle terms cancel and so we are left with this as our final answer:
4y^2-121
