Rút gọn các biểu thức sau: (a) A(x)=−5x(2x^3−3x^2+x−4) (b) B(x)=(6x^3+4x^2−6x):(2x)+(2x−1)(x^2+5)

a) \(A\left( x \right) = - 5x\left( {2{x^3} - 3{x^2} + x - 4} \right)\)

\[A(x) = - 10{x^4} + 15{x^3} - 5{x^2} + 20x\]

b) \(B\left( x \right) = \left( {6{x^3} + 4{x^2} - 6x} \right):\left( {2x} \right) + \left( {2x - 1} \right)\left( {{x^2} + 5} \right)\)

\[B\left( x \right) = 3{x^2} + 2x - 3 + 2{x^3} + 10x - {x^2} - 5\]

\[B\left( x \right) = 2{x^3} + 2{x^2} + 12x - 8\]