If A= 3 9 + 9 27 + 27 81 and B= 81 - 3 , then BA is equal to .
Answer
2
Solution
First simplify the difference
3 - = 3 - 3 3 = 2 3 = 2 3
so 3 = 12( 3 - ). Using this for = 3 , 9 , 27 , the sum telescopes:
A = 12 [( 9 - 3 ) + ( 27 - 9 ) + ( 81 - 27 ) ]
A = 12( 81 - 3 ) = B2
∴ BA = 2
Answer: 2