Question

Subtract a³-a3² from b³-b3²

Answer 1

Answer:

: a³-b³= (a-b)(a²+ab+ b²)

Expressed in words, the difference of the cubes of two quantities is the product of the difference of the two quantities by the “imperfect square of the sum.”

Proof:

We know the well-known formula

(a-b)³=a³-3 a²b+3 ab²-b³

By transposition,

a³ - b³ = (a-b)³ + 3 a²b - 3 ab²

a³ - b³ = (a-b)³ +3 ab(a-b)

a³ - b³ = (a-b) [(a-b)² +3 ab]

a³ - b³ = (a-b) [(a-b)² +3 ab]

We all know (a - b)² = a² - 2 ab + b²

So

a³ - b³ = (a-b) [(a² - 2 ab + b²) +3 ab]

a³-b³= (a-b)(a²+ab+ b²) [Proved]