Question

Factorise : 9(a - 2)2- 16(a + 2)2

Answer 1

9(a - 2)2- 16(a + 2)2= [ 3( a - 2 )]2 - [4( a + 2 )]2
= [ 3( a - 2 ) - 4( a + 2 )][ 3( a - 2) + 4( a + 2 )]

             [  a2 - b2 = ( a + b )( a - b )]  

= [ 3a - 6 - 4a - 8 ][ 3a - 6 + 4a + 8 ]
= ( - a - 14 )( 7a + 2 )
= - ( a + 14 )( 7a + 2 )