Question

tính B = (3x+1) x (3 bình +1 ) .... + (3 mu 64 +1 ) +1

cần gấp 

Answer 1

B = (3x + 1) x (3² + 1 ) .... + (1 +  3⁶⁴) + 1

= (1 + 3)(1 + 3²) ....(1 + 3⁶⁴) + 1

= \(\dfrac{1}{2} . 2 .(1 + 3) (1 + 3\)²) ...... (1 + 3⁶⁴) + 1

= \(\dfrac{1}{2}.(3\)² - 1) (1 + 3²) (1 + 3⁴) ....(1 + 3⁶⁴) + 1

= ...........

= \(\dfrac{1}{2}.\) (3⁶⁴ - 1) (1 + 3⁶⁴) + 1

= \(\dfrac{1}{2}.\) (3¹²⁸ - 1) + 1

= \(\dfrac{1}{2}.\) 3¹²⁸ - 1/2 + 1

= \(\dfrac{1}{2}.\) 3¹²⁸ + \(\dfrac{1}{2}\) 

= 1/2 (3¹²⁸ + 1)

= 3¹²⁸ + 1/2