Ta có: 

\(A=1+2.6+3.6^2+4.6^3+...+100.6^{99}\)

=> \(6A=6+2.6^2+3.6^3+....+99.6^{99}+100.6^{100}\)

=> A - 6A = \(1+6+6^2+6^3+...+6^{99}-100.6^{100}\)

=> \(-5A=1+6+6^2+...+6^{99}-100.6^{100}\)

Đặt: \(B=1+6+6^2+...+6^{99}\)

=> \(6B=6+6^2+6^3+...+6^{100}\)

=> 6 B - B = \(6^{100}-1\)

=> B = \(\frac{6^{100}-1}{5}\)

=> \(-5A=\frac{6^{100}-1}{5}-100.6^{100}\)

=> \(A=\frac{499.6^{100}+1}{25}\)

nhào vô  $$$$$$$$$$ cho money

Trả lời :

Bn HACK NICK FRÉ FIRE đừng bình luận linh tinh nhé !

- Hok tốt !

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6^2.(6+3)+3^3/-13=36.3^2+3^3/-13=3^2(36+3)/-13=9.39/-13=-27

2^10.3^8-2.3^9.2^9 / 2^10.3^8+3^8.2^8.2^2.5

=2^10.3^8(1-3) / 2^10.3^8(1+5)

=-2/6=-1/3

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

bạn tham khảo nha