Question

tính tổng:

A=4+2^2+2^3+2^4+......+2^20

S=3^0+3^2+3^4+2^6+....+3^2002

B=2^1+2^2+2^3+....+2^60

Answer 1

A = 4 + (2² + 2³ + 2⁴ + ... + 2²⁰)

A - 4 = 2² + 2³ + 2⁴ + ... + 2²⁰

2(A - 4) = 2³ + 2⁴ + 2⁵ + ... + 2²¹

A - 4 = 2(A - 4) - (A - 4) = (2³ + 2⁴ + 2⁵ + ... + 2²¹) - (2² + 2³ + 2⁴ + ... + 2²⁰)

A - 4 = (2³ - 2³) + (2⁴ - 2⁴) + ... + (2²⁰ - 2²⁰) + (2²¹ - 2²)

A - 4 = 2²¹ - 4

A = 2²¹ - 4 + 4

A = 2²¹

Answer 2

A=2^21.Duyệt nha

Answer 3

A=4+2^2+2^3+2^4+...+2^20

2A=2^3+2^3+2^4+2^5+...+2^21

2A-A=2^3+2^3+2^4+2^5+...+2^21-2^2-2^2-2^3-2^4-...-2^20

3A=2^21+2^3-2^2-2^2

A=2^21:3

S=1+3^2+3^4+3^6+...+3^2002

3^2S=3^2+3^4+3^6+3^8+...+3^2004

3^2S-S=3^2+3^4+3^6+3^8+..+3^2004-1-3^2-3^4-3^6-...-3^2002

8S=3^2004-1

S=(3^2004-1):8

B=2^1+2^2+2^3+...+2^60

2B=2^2+2^3+2^4+...+2^61

2B-B=2^2+2^3+2^4+...+2^61-2^1-2^2-2^3-...-2^60

B=2^61-2=2(2^60-1)

Answer 4

nhầm câu 2A-A=2^21=> A=2^21

Answer 5

2^{21 nha ban} 

 ^{dung cho minh nhe}

Answer 6

^ là sao ạk

Answer 7

2^{555555555555555555}