Câu hỏi:

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1. Thực hiện phép tính:

a) 143  .  126143  .  26143\,\,.\,\,126 - 143\,\,.\,\,26;                                               b) 3  .  26  .  1253\,\,.\,\,{2^6}\,\,.\,\,125.

2. Tìm xx, biết:

a) 20(x+1)=1020 - (x + 1) = 10;                                             b) 6+10x=47:456 + 10x = {4^7}:{4^5}.

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Lời giải

Hướng dẫn giải:

1. a) 62  .  12362  .  2362\,\,.\,\,123 - 62\,\,.\,\,23=62  .  (12323) = 62\,\,.\,\,\left( {123 - 23} \right)=62  .  100=6200 = 62\,\,.\,\,100 = 6200.

b) 3  .  26  .  1253\,\,.\,\,{2^6}\,\,.\,\,125=3  .  26  .  125=3  .  23  .  (23  .  125) = 3\,\,.\,\,{2^6}\,\,.\,\,125 = 3\,\,.\,\,{2^3}\,\,.\,\,\left( {{2^3}\,\,.\,\,125} \right)

=3  .  8  .  (8  .  125)=24  .  1  000=24  000 = 3\,\,.\,\,8\,\,.\,\,\left( {8\,\,.\,\,125} \right) = 24\,\,.\,\,1\,\,000 = 24\,\,000.

2. 

a) 20(x+1)=1020 - (x + 1) = 10

x+1=2010x + 1 = 20 - 10

x+1=10x + 1 = 10

x=101x = 10 - 1

x=9x = 9

Vậy x=9x = 9.

b) 6+10x=47:456 + 10x = {4^7}:{4^5}

6+10x=426 + 10x = {4^2}

6+10x=166 + 10x = 16

10x=16610x = 16 - 6

10x=1010x = 10

x=1x = 1

Vậy x=1x = 1.

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