Giải thích các bước giải:
\(\begin{array}{l}
1.\,\,{\left( {6x + 1} \right)^2} + {\left( {6x - 1} \right)^2} - 2\left( {1 + 6x} \right)\left( {6x - 1} \right)\\
= {\left[ {\left( {1 + 6x} \right) - \left( {6x - 1} \right)} \right]^2} = {\left( {1 + 6x - 6x + 1} \right)^2}\\
= 4\\
2.\,\,\,3x\left( {x - 2} \right) - 5x\left( {1 - x} \right) - 5\left( {{x^2} - 3} \right)\\
= 3{x^2} - 6x - 5x + 5{x^2} - 5{x^2} + 15\\
= 3{x^2} - 11x + 15\\
3.\,\,\,\left( {7x - 3} \right)\left( {2x + 1} \right) - \left( {5x - 2} \right)\left( {x + 4} \right) - 9{x^2} + 17x\\
= 14{x^2} + x - 3 - \left( {5{x^2} + 18x - 8} \right) - 9{x^2} + 17x\\
= 5\\
4.\,\,\left( {6x - 5} \right)\left( {x + 8} \right) - \left( {3x - 1} \right)\left( {2x + 3} \right) - 9\left( {4x - 3} \right)\\
= 6{x^2} + 43x - 40 - \left( {6{x^2} + 7x - 3} \right) - 36x + 27\\
= - 10
\end{array}\)
