Respostas

  • Usuário do Brainly
2013-02-26T18:34:30-03:00

Observe que:

 

(\text{a}-\text{b})^3=\text{a}^3-3\text{a}^2\text{b}+3\text{a}\text{b}^2-\text{b}^3

 

Desta maneira, se \text{a}=2\text{x} e \text{b}=\text{y}, temos que:

 

(2\text{x}-\text{y})=(2\text{x})^3-3\cdot(2\text{x})^2\cdot\text{y}+3\cdot2\text{x}\cdot(\text{y})^2-\text{y}^3

 

(2\text{x}-\text{y})=8\text{x}^3-12\text{x}^2\text{y}+6\text{x}\text{y}^2-\text{y}^3

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