Toán Lớp 7: Chứng minh đẳng thức x^2 – 4 + ( x – 2 )^2 = 2x ( x – 2 )
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Toán Lớp 7: Chứng minh đẳng thức x^2 – 4 + ( x – 2 )^2 = 2x ( x – 2 )
Comments ( 1 )
{x^2} – 4 + {\left( {x – 2} \right)^2}\\
= {x^2} – 4 + \left( {x – 2} \right).\left( {x – 2} \right)\\
= {x^2} – 4 + {x^2} – 2x – 2x + 4\\
= 2{x^2} – 4x\\
= 2x.\left( {x – 2} \right)\\
Vậy\,{x^2} – 4 + {\left( {x – 2} \right)^2} = 2x\left( {x – 2} \right)
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