Đáp án:
\(\begin{array}{l}
2)B = {x^2} + 4x - 24\\
3)C = 4x - 25\\
4)D = 12x + 10\\
5)E = - 20{x^2} - 100x - 240\\
6)F = - 18{x^3} - 46{x^2} - 8x + 16
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
2)B = {x^2} - 4x + 4 + 8x - 28\\
= {x^2} + 4x - 24\\
3)C = {x^2} - 25 + 4{x^2} + 4x + 1 - 5{x^2}\\
= 4x - 25\\
4)D = 4{x^2} + 12x + 9 - 4{x^2} + 1\\
= 12x + 10\\
5)E = 5.\left( { - 2} \right).{\left( {x + 5} \right)^2} - 10\left( {x - 1} \right)\left( {x + 1} \right)\\
= - 10\left( {{x^2} + 10x + 25} \right) - 10{x^2} + 10\\
= - 10{x^2} - 100x - 250 - 10{x^2} + 10\\
= - 20{x^2} - 100x - 240\\
6)F = {x^2} + 10x + 25 - 4x\left( {4{x^2} + 12x + 9} \right) - \left( {2x - 1} \right)\left( {{x^2} - 9} \right)\\
= {x^2} + 10x + 25 - 16{x^3} - 48{x^2} - 36x - 2{x^3} + 18x + {x^2} - 9\\
= - 18{x^3} - 46{x^2} - 8x + 16
\end{array}\)