Thu gọn đa thức sau: a ) 3x^2 y ( 2x^2 - y ) - 4x^2 ( x^2 y - y^2)

a) \(3{x^2}y\left( {2{x^2} - y} \right) - 4{x^2}\left( {{x^2}y - {y^2}} \right)\)

\( = 6{x^4}y - 3{x^2}{y^2} - 4{x^4}y + 4{x^2}{y^2}\)

\( = 2{x^4}y + {x^2}{y^2}.\)

b) \(3x\left( {x - 2} \right) - 5x\left( {1 - x} \right) - 8\left( {{x^2} - 3} \right)\)

\( = 3{x^2} - 6x - 5x + 5{x^2} - 8{x^2} + 24\)

\( = - 11x + 24.\)