y^3 + y^2 - 4y - 4
factor by grouping the first two and the last two. Be careful with the second grouping because of the _(-) in front of the 4y.
(y^3 +y^2) + (-4y -4)
Take out the common factors:
y^2(y+1) + -4(y+1)
See the y+1?
Write that down once and your other factor is what is left over.
You can multiply these factors to check that you did it correctly.
t^2 + 4z^2
This is a sum of two squares and it cannot be factored.
You can factor a difference of two squares. If this was t^2 -4z^2
it would factor to (t-2z)(t+2z)