Toán Lớp 6: a,-23+X=-1
B,X-17=-17
C,X:15:X:20 VÀ 50
đ,484+x=-632+(-548)
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Toán Lớp 6: a,-23+X=-1
B,X-17=-17
C,X:15:X:20 VÀ 50
đ,484+x=-632+(-548)
Comments ( 1 )
a) – 23 + x = – 1\\
\Leftrightarrow x = – 1 + 23\\
\Leftrightarrow x = 22\\
Vậy\,x = 22\\
b)x – 17 = – 17\\
\Leftrightarrow x = – 17 + 17\\
\Leftrightarrow x = 0\\
Vậy\,x = 0\\
c)x \vdots 15;x \vdots 20\\
\Leftrightarrow x = BC\left( {15;20} \right)\\
+ 15 = 3.5\\
+ 20 = {2^2}.5\\
\Leftrightarrow BCNN\left( {15;20} \right) = {2^2}.3.5 = 60\\
\Leftrightarrow x \in \left\{ {60;120;…} \right\}\\
Do:50 < x < 70\\
\Leftrightarrow x = 60\\
d)30 \vdots x;45 \vdots x\\
\Leftrightarrow x = UC\left( {30;45} \right)\\
+ 30 = 2.3.5\\
+ 45 = {3^2}.5\\
\Leftrightarrow UCLN\left( {30;45} \right) = 3.5 = 15\\
\Leftrightarrow x \in \left\{ {1;3;5;15} \right\}\\
x > 10\\
\Leftrightarrow x = 15\\
d)484 + x = – 632 + \left( { – 548} \right)\\
\Leftrightarrow 484 + x = – 1180\\
\Leftrightarrow x = – 1180 – 484\\
\Leftrightarrow x = – 1664\\
Vậy\,x = – 1664
\end{array}$