Math

• (x + y)² = x² + 2xy + y²
• (x – y)² = x² – 2xy + y²
• x² – y² = (x + y) (x – y)
• (x + a) (x + b) = x² + (a + b) x + ab
• (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx
• (x + y)³ = x³ + 3x²y + 3xy² + y³ = x³ + y³ + 3xy (x + y)
• (x – y)³ = x³ – 3x²y + 3xy² – y³ = x³ – y³ – 3xy (x – y)
• x³ + y³ = (x + y) (x² – xy + y² )
• x³ – y³ = (x – y) (x² + xy + y² )
• x³ + y³ + z³ – 3xyz = (x + y + z) (x² + y² + z² – xy – yz – zx)