Question

Cho : M= 1 + 5 + 5² + 5³ + ..............+ 5²¹

Tính giá trị biểu thức 4M + 4

Answer 1

M = 1 + 5 + 5² +....+ 5²¹

5M = 5 + 5² + .... + 5²²

5M - M = 5²² - 1

4M = 5²² - 1 

4M + 4 = 5²² - 1 + 4

4M + 4 = 5²² + 3

Answer 2

Ta có : M = 1 + 5 + 5² + 5³ + ..... + 5²¹ 

=> 5M = 5 + 5² + 5³ + ..... + 5²²  

=> 5M - M = 5²² - 1

=> 4M = 5²² - 1

=> 4M + 4 = 5²² - 1 + 4

=> 4M + 4 = 5²² + 3 

Answer 3

M = 1 + 5 + 5² + 5³ + ....... + 5²¹

5M = 5 + 5² + 5³ + ....... + 5²¹ + 5²²

5M - M = (5 + 5² + 5³ + ....... + 5²¹ + 5²²) - (1 + 5 + 5² + 5³ + ....... + 5²¹)

4M = 5²² - 1

M = \(\frac{5^{22}-1}{4}\)

4M = \(\frac{5^{22}-1}{4}.4+4=5^{22}-1+4=5^{22}+3\)

Answer 4

M = 1 + 5 + 5² +....+ 5²¹

5M = 5 + 5² + .... + 5²²

5M - M = 5²² - 1

4M = 5²² - 1 

4M + 4 = 5²² - 1 + 4

4M + 4 = 5²² + 3

Answer 5

M = 1 + 5 + 5² +....+ 5²¹

5M = 5 + 5² + .... + 5²²

5M - M = 5²² - 1

4M = 5²² - 1 

4M + 4 = 5²² - 1 + 4

4M + 4 = 5²² + 3

Answer 6

M = 1 + 5 + 5² +....+ 5²¹

5M = 5 + 5² + .... + 5²²

5M - M = 5²² - 1

4M = 5²² - 1 

4M + 4 = 5²² - 1 + 4

4M + 4 = 5²² + 3