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Bài 5: rút gọn
(x +1)^2 – (2x + 1)^2

User RobertL
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1 Answer

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(x+1)^2-(2x+1)^2=\\\\=(x^2+2\cdot x\cdot1+1^2)-((2x)^2+2\cdot2x\cdot1+1^2)=\\\\=(x^2+2x+1)-(4x^2+4x+1)=\\\\=x^2+2x+1-4x^2-4x-1=\\\\=x^2-4x^2+2x-4x+1-1=\boxed{-3x^2-2x}

User Andre Kostur
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