Răspuns :
a=9x²-12x+4+24x-18x²-16+12x+16-24x+9x²
a=4(dupa reducerea termenilor asemenea:9x²+9x²-18x²=0;12x-12x=0;24x-24x=0;si 16-16=0)
a=4(dupa reducerea termenilor asemenea:9x²+9x²-18x²=0;12x-12x=0;24x-24x=0;si 16-16=0)
... = (3x-2)² + 2*(3x-2) *(4-3x) + (4-3x)² = (3x-2 + 4-3x)²
conform formulei ↓ ↓ ↓ ↓
a² + 2 * a * b + b² = a² + b²
↓
... = (2)² = 4 ∈ Z
conform formulei ↓ ↓ ↓ ↓
a² + 2 * a * b + b² = a² + b²
↓
... = (2)² = 4 ∈ Z