1) Analyzing those trinomials, a perfect square trinomial must satisfy some conditions like (ax+b)²
2) Given
y² +12y +144 ≠ (y +6)²
y² +20y +100 = (y+10)²
y²-16y +64 =(y-8)²
y² +10y +25 = (y +5)²
3) So since b/2=12/2 = 6 ≠ 12² in the y² +12y +144 is different from 12², then
y² +12y +144 is not a perfect square trinomial.
