[Toán 7] Tìm 3 số

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nguyenan_0201

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phankyanhls2000

Thay $b=\frac{3}{2}a$ , $c=2a$ vào $a^2-b^2+2c^2 =108$
Ta có:
$a^2-(\frac{3}{2}a)^2+2(2a)^2=108$
\Leftrightarrow$6,75a^2=108$
\Leftrightarrow$a^2=16$
\Leftrightarrow$a=4$
 
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