Let = (1 - 2 ( 11 ) ) (1 - 2 ( 3 11 ) ) (1 - 2 ( 9 11 ) ) (1 - 2 ( 27 11 ) ) (1 - 2 ( 81 11 ) ). Then the value of 5 - 2 is .
Answer
3.9 to 4.1
Solution
Identity: 1 - 2 = - 3 2 2 (since 4 2 2 - 3 = 2 - 1).
With k = 3k 11, k = 0, , 4, the product telescopes:
= (-1)5 35 22 22
243 22 = 11 + 22 243 22 = - 22
= (-1)(-1) = 1, so 5 - 2 = 4
Answer: 4