Answer:
(y+5)²
Step-by-step explanation:
Every perfect square trinomial, completes the rule:
(a+b)²=(a²+2ab+b²)
Let's complete the PST:
(a) would be the square root of y², which is y.
(b) would be a number that multiplied by 2y gives us 10y, which is 5.
Our perfect square trinomial is y²+10y+25
Finally, using the mentioned rule, the binomial square for that equation is (y+5)²
