Toán Lớp 6: 3,20 Bỏ ngoặc rồi tính tổng sau
a, (-28)+(-35)-92+(-82)
b, 15-(-38)+(-55)-(+47)
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Toán Lớp 6: 3,20 Bỏ ngoặc rồi tính tổng sau
a, (-28)+(-35)-92+(-82)
b, 15-(-38)+(-55)-(+47)
Comments ( 2 )
a)\;\left( { – 28} \right) + \left( { – 35} \right){\rm{ }} – {\rm{ }}92 + \left( { – 82} \right)\\
\begin{array}{*{20}{l}}
{ = – 28{\rm{ }} – {\rm{ }}35{\rm{ }} – {\rm{ }}92{\rm{ }} – {\rm{ }}82\;}\\
{ = {\rm{ }} – {\rm{ }}\left( {28{\rm{ }} + {\rm{ }}35{\rm{ }} + {\rm{ }}92{\rm{ }} + {\rm{ }}82} \right)}\\
{ = {\rm{ }} – {\rm{ }}\left[ {\left( {28{\rm{ }} + {\rm{ }}82} \right){\rm{ }} + {\rm{ }}\left( {35{\rm{ }} + {\rm{ }}92} \right)} \right]}\\
{ = {\rm{ }} – {\rm{ }}\left( {110{\rm{ }} + {\rm{ }}127} \right)}\\
{ = {\rm{ }} – 237}
\end{array}\\
\begin{array}{*{20}{l}}
{b)15{\rm{ }} – {\rm{ }}\left( { – 38} \right){\rm{ }} + {\rm{ }}\left( { – 55} \right){\rm{ }} – {\rm{ }}\left( { + 47} \right)}\\
{ = {\rm{ }}15{\rm{ }} + {\rm{ }}38{\rm{ }} – {\rm{ }}55{\rm{ }} – {\rm{ }}47}\\
{ = {\rm{ }}53{\rm{ }} – {\rm{ }}55{\rm{ }} – {\rm{ }}47}\\
{ = {\rm{ }} – \left( {55{\rm{ }} – {\rm{ }}53} \right){\rm{ }} – {\rm{ }}47}\\
{ = {\rm{ }} – 2{\rm{ }} – {\rm{ }}47}\\
{ = {\rm{ }} – \left( {2{\rm{ }} + {\rm{ }}47} \right)}\\
{ = {\rm{ }} – 49}
\end{array}\\
\end{array}\]