Se aplica formula:
(a + b)³ = a³ + 3a²b + 3ab² + b³
Nu trebuie s-o tii minte. O poti deduce in felul urmator
(a + b)³ = (a + b)(a + b)(a + b) = (a² + 2ab + b²)(a + b) = a³ + 3a²b + 3ab² + b³
a) (3x + 1)³ = (3x)³ + 3(3x)²(1) + 3(3x)(1)² + (1)³ = 27x³ + 27x² + 9x + 1
b) (2t + z²)³ = (2t)³ + 3(2t)² (z²) + 3(2t)(z²)² + (z²)³ =8t³ + 12t²z² + 6tz⁴ + z⁶