Thực hiện phép tính (tính hợp lí nếu có thể): a) [ ( 5^2 ⋅ 2^3 − 7^2 ⋅ 2 ) : 2 ] ⋅ 6 − 3^ 2 ⋅ 17.

1) a) \(\left[ {\left( {{5^2} \cdot {2^3} - {7^2} \cdot 2} \right):2} \right] \cdot 6 - {3^2} \cdot 17\)

\( = \left[ {\left( {{5^2} \cdot {2^2} - {7^2}} \right) \cdot 2:2} \right] \cdot 6 - {3^2} \cdot 17\)

\( = \left[ {\left( {25 \cdot 4 - 49} \right) \cdot 1} \right] \cdot 6 - {3^2} \cdot 17\)

\( = \left( {100 - 49} \right) \cdot 6 - 3 \cdot 3 \cdot 17\)

\( = 51 \cdot 6 - 3 \cdot 51\)

\( = 51 \cdot \left( {6 - 3} \right)\)

\( = 51 \cdot 3 = 153.\)

b) \[53 \cdot 39 + 47 \cdot 39 - 53 \cdot 21 - 47 \cdot 21\]

\[ = \left( {53 \cdot 39 + 47 \cdot 39} \right) - \left( {53 \cdot 21 + 47 \cdot 21} \right)\]

\[ = 39 \cdot \left( {53 + 47} \right) - 21 \cdot \left( {53 + 47} \right)\]

\[ = 39 \cdot 100 - 21 \cdot 100\]

\[ = 3\,\,900 - 2\,\,100\]

\[ = 1\,\,800\].