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tuongvy28082011
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Câu 5: Cho biểu thức A = 2x - 2/xy +y-2/x+3. Hỏi A có giá trị nhỏ nhất hay không? Vì sao?

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Ng Cao Nanh
4 tháng trước

Đáp án: Min A= 2

 

Giải thích các bước giải:

A= 2x - 2√xy + y - 2√x + 3

A= x + x - 2√xy + y - 2√x + 1 + 2

A=(x - 2√xy +y) + (x - 2√x +1 ) + 2

A=(√x - √y)² + (√x - 1)² + 2

(√x - √y)² + (√x - 1)² ≥ 0

⇒ Min A = 2

Chúc em học tốt

 

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