Toán Lớp 8: Rút gọn: A = (x-2)^2 -(x-1)(x+1) .
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Toán Lớp 8: Rút gọn: A = (x-2)^2 -(x-1)(x+1) .
Comments ( 2 )
{(x – 2)^2} – (x – 1)(x + 1)\\
= \left( {{x^2} – 4x + 4} \right) – \left( {{x^2} – 1} \right)\\
= {x^2} – 4x + 4 – {x^2} + 1\\
= \left( {{x^2} – {x^2}} \right) – 4x + \left( {4 + 1} \right)\\
= 5 – 4x
\end{array}\]