1 - 8a3= (1)3 - (2a)3= ( 1 - 2a )[ (1)2 + 1 x 2a + (2a)2 ] [ ∵ a3 - b3 = ( a - b )( a2 + ab + b2 )]= ( 1 - 2a )[ 1 + 2a + 4a2 ]

English

Factorise : 1 - 8a3 - Mathematics

Factorise : 1 - 8a³

Sum

1 - 8a³= (1)³ - (2a)³
= ( 1 - 2a )[ (1)² + 1 x 2a + (2a)² ]
[ ∵ a³ - b³ = ( a - b )( a² + ab + b² )]
= ( 1 - 2a )[ 1 + 2a + 4a² ]

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Method of Factorisation : the Sum Or Difference of Two Cubes

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Chapter 5: Factorisation - Exercise 5 (D) [Page 74]

Chapter 5 Factorisation
Exercise 5 (D) | Q 2 | Page 74