Răspuns:
(a + b)² = a² + 2ab + b²
a) x² + 2xy + y² = (x + y)²
b) x² + 2x + 1 = x² + 2 × 1 × x + 1² = (x + 1)²
c) x² + 4x + 4 = x² + 2 × 2 × x + 2² = (x + 2)²
d) y² + 6y + 9 = y² + 2 × 3 × y + 3² = (y + 3)²
e) x² + 8x + 16 = x² + 2 × 4 × x + 4² = (x + 4)²
f) b² + 10b + 25 = b² + 2 × 5 × b + 5² = (b + 5)²
g) x² + 12x + 36 = x² + 2 × 6 × x + 6² = (x + 6)²
h) 4x² + 12x + 9 = (2x)² + 2 × 2x × 3 + 3² = (2x + 3)²
i) 9x² + 12x + 4 = (3x)² + 2 × 3x × 2 + 2² = (3x + 2)²
-Mihai