đăng cái này làm gì ?

làm đc k

Câu 2:

A = 1.3 + 3.5 + 5.7 + ...+ 97.99 + 99.100

A = (1.3 + 3.5 + 5.7 + ...+ 97.99) + 99.100

Đặt B = 1.3 + 3.5 + 5.7 + ...+ 97.99

6B = B = 1.3 + 3.5 + 5.7 + ...+ 97.99

6B = 1.3.6 + 3.5.6 + ...+ 97.99.6

6B = 1.3.(5+1) . 3.5.(7-1) + ..+97.99.(101-95)

6B = 1.3.5 + 1.3.1 +3.5.7- 1.3.5 +...+97.99.101-95.99.97

6B = 1.3.1 + 97.99.101

6B = 3 + 969903

6B = 969906

B = 969906 : 6

B = 161651

A = 161651 + 99.100

A = 161651 + 9900

A = 171551

Câu 3:

A = A = 2.4 + 4.6 + 6.8 +...+ 98.100 + 100.102

6A = 2.4.6 + 4.6.6 +..+98.100.6 + 100.102.6

6A = 2.4.6 + 4.6.(8-2) +...+100.102.(104 - 98)

6A = 2.4.6 + 4.6.8 - 2.4.6 + ...+ 100.102.104 - 98.100.102

6A = 100.102.104

A = 100.102.104 : 6

A = 10200.104 : 6

A = 1060800 : 6

A = 176800

A = 1/2 + 1/4 + 1/8 + ... + 1/128

A = 1/2^1 + 1/2^2 + 1/2^3 + ... + 1/2^7

2A = 1 + 1/2 + 1/2^2 + ... + 1/2^6

2A - A = 1 - 1/2^7 = A

G = 5 - 5^2/1*6  5^2/6*11 - ... - 5^2/101*106

G = -5(-1 + 5/1*6 + 5/6*11 + ... + 5/101*106)

G = -5(-1 + 1 - 1/6 + 1/6 - 1/11 + ... + 1/101 - 1/106)

G = -1.(-1/106)

G = 1/106

a)\(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}=\frac{\left(2^2\right)^5.\left(3^2\right)^4-2.\left(2.3\right)^9}{2^{10}.3^8+\left(3.2\right)^8.2^2.5}=\frac{2^{10}.3^8-2.2^9.3^9}{2^{10}.3^8+3^8.2^8.2^2.5}=\frac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+3^8.2^{10}.5}\)

\(=\frac{2^{10}.3^8.\left(1-3\right)}{2^{10}.3^8.\left(1+5\right)}=\frac{-2}{6}=\frac{-1}{3}\)

b) đặt A=2¹⁰⁰ - 2⁹⁹ + 2⁹⁸ - 2⁹⁷ +...+ 2² - 2

=>2A=2¹⁰¹-2¹⁰⁰+2⁹⁹-2⁹⁸+...+2³-2²

=>2A+A=2¹⁰¹-2¹⁰⁰+2⁹⁹-2⁹⁸+...+2³-2²+2¹⁰⁰ - 2⁹⁹ + 2⁹⁸ - 2⁹⁷ +...+ 2² - 2

=>3A=2¹⁰¹-2

=>A=\(\frac{2^{101}-2}{3}\)

thank kiu 

thank kiu

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