Which trinomial is a perfect square trinomial? y2 + 6y + 36 y2 + 18y + 81 y2 + 50y + 100 y2 + 25y + 200

Out of the four trinomials, y^2+18y+81 is correct.
Step By Step
To determine a perfect square trinomial, the first and third terms have to be square roots and the middle term has to be two times the square root of the third term.

y^2 is a square root and 81 is a square root.
y^2 simplifies to y and 81 simplifies to 9.
It would be y+18y+9
The third term is 9, so multiply that by two and you get 18!
Therefore, that is correct!
y^2+18y+81 is a perfect square trinomial!

Hope this helps!