Question

what is the expansion of (5a-3b)³​

Answer 1

As we know ,

( x – y )³ = x³ – 3x²y + 3xy² – y³

OR

( x – y )³ = ( x – y ) ( x² + y² – 2xy )

Now , ( 5a – 3b )³

= (5a)³ – 3(5a)²(3b) + 3(5a)(3b)² – (3b)³

= 125a³ – 225a²b + 135ab² – 27b²

OR

( 5a – 3b )³

= ( 5a – 3b ) [ (5a)² + ( 3b)² – 2( 5a )( 3b ) ]

= ( 5a – 3b ) ( 25a² + 9b² – 30ab )

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