(2,0 điểm) Thực hiện phép tính (tính hợp lí nếu có thể): a) 160 − ( 4 ⋅ 5 2 − 3 ⋅ 2 3 ) . b) ( − 25 ) + 15 + ( − 17 ) − ( − 25 ) + ( − 13 ) . c) 47 ⋅ 8 − 27 ⋅ 9 + 47 ⋅ 12 − 27 ⋅ 11

a) \(160 - \left( {4 \cdot {5^2} - 3 \cdot {2^3}} \right)\)

\( = 160 - \left( {4.25 - 3.8} \right)\)

\( = 160 - \left( {100 - 24} \right)\)

\( = 160 - 100 + 24\)

\( = 60 + 24\)

\( = 84\).

c) \(47 \cdot 8 - 27 \cdot 9 + 47 \cdot 12 - 27 \cdot 11\)

\( = \left( {47 \cdot 8 + 47 \cdot 12} \right) - \left( {27 \cdot 9 + 27 \cdot 11} \right)\)

\( = 47 \cdot \left( {8 + 12} \right) - 27 \cdot \left( {9 + 11} \right)\)

\( = 47 \cdot 20 - 27 \cdot 20\)

\( = 20 \cdot \left( {47 - 27} \right)\)

\( = 20 \cdot 20\)

\( = 400\).

b) \(\left( { - 25} \right) + 15 + \left( { - 17} \right) - \left( { - 25} \right) + \left( { - 13} \right)\)

\[ = \left[ {\left( { - 25} \right) + 25} \right] + \left[ {\left( { - 17} \right) + \left( { - 13} \right)} \right] + 15\]

\[ = 0 + \left( { - 30} \right) + 15\]

\( = - 15\).

d) \[\left( { - 134} \right) + 51 \cdot 134 + \left( { - 134} \right) \cdot 48\]

\[ = 134 \cdot \left( { - 1} \right) + 51 \cdot 134 + 134 \cdot \left( { - 48} \right)\]

\[ = {\rm{ }}134 \cdot \left[ {\left( { - 1} \right) + 51 + \left( { - 48} \right)} \right]\]

\[ = 134 \cdot 2\]

\[ = 168.\]