Question

Write the following cube in expanded form:- (2a – 3b)³ 

Answer 1

It is known that,

(a + b)³ = a³ + b³ + 3ab(a + b)  and  (a - b)³ = a³ - b³ - 3ab(a - b)

(2a−3b)³= (2a)³−(3b)³–(3×2a×3b)(2a–3b)

             = 8a³–27b³–18ab(2a–3b)

             = 8a³–27b³–36a2b+54ab2