Question

what is the formula of a cube plus b cube

Answer 1

 The algebraic formula is

(a ³ + b ³) = (a+b)(a2-ab+b2)

Eg.

x³ + 2 ³   = (x + 3) ((x)² - x(3) + 3 ²)

               = (x+3) (x² - 3x + 9)

There fore the expansion of x³ + 2 ³ is (x+3) (x² - 3x + 9)

Answer 2

a³ + b³ = (a + b)³ - 3 a b (a + b)

(a + b)³ = a³ + 3 a² b + 3 a b² + b³

            = a³ + b³+ 3 a b (a + b)

(a + b)³ - 3 a b (a + b) = a³ + b³

a³ + b³ = (a + b)³ - 3 a b (a + b)