Toán Lớp 8: (X-2)^2-x(x-1)
(X-4)^2-x^2=0
(X-4)^2-x^2=8
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Toán Lớp 8: (X-2)^2-x(x-1)
(X-4)^2-x^2=0
(X-4)^2-x^2=8
Comments ( 2 )
a){\left( {x – 2} \right)^2} – x\left( {x – 1} \right)\\
\Rightarrow {x^2} – 2.x.2 + {2^2} – x.x + ( – x).( – 1)\\
\Rightarrow {x^2} – 4x + 4 – {x^2} + x\\
\Rightarrow ({x^2} – {x^2}) – (4x – x) + 4\\
\Rightarrow – 3x + 4\\
b){(x – 4)^2} – {x^2} = 0\\
\Rightarrow (x – 4 – x)(x – 4 + x) = 0\\
\Rightarrow – 4.(2x – 4) = 0\\
\Rightarrow 2x – 4 = 0\\
\Rightarrow x = 2\\
c){(x – 4)^2} – {x^2} = 8\\
\Leftrightarrow – 4.(2x – 4) = 8\\
\Leftrightarrow 2x – 4 = – 2\\
\Leftrightarrow 2x = 2\\
\Leftrightarrow x = 1
\end{array}\]