(1) (a + b)² = a² + 2ab + b²
(2) (a + b)² = (a – b)² + 4ab
3) (a – b)² = a² – 2ab + b²
4) (a – b)² = (a + b)² – 4ab
5) a² + b² = (a + b)² – 2ab
6) a² + b² = (a – b)² + 2ab
7) a² – b² =(a + b)(a – b)
8) 2(α² + в²) = (a + в)² + (a – в)²
9) 4ab = (a + b)² -(a – b)²
10) ab = {(a + b)/2}² – {(a – b)/2}²
11) (a + b + c)² = a² + b² + c² + 2(ab + bc + ca)
12) (a + b)³ = a³ + 3a²b + 3ab² + b³
13) (a + b)³ = a³ + b³ + 3ab (a + b)
14) (a – b)³= a³ – 3a²b + 3ab² – b³
15) a³ + b³ = (a + b) (a² – ab + b²)
16) a³ + b³ = (a + b)³ – 3ab (a + b)
17) a³ -b³ = (a – b) (a² + ab + b²)
(18) a³ – b³ = (a – b)³ + 3ab (a – b)
( 19) (a + b + c)² = a² + b² + c² + 2(ab + bc + ca)
