Thực hiện phép tính (a) 5ab^3(2a^2b−a^3+1/5a^2) (b) 2xy(x^2−y)+x(2y^2−y)−2x^3y−1

a) \(5a{b^3}\left( {2{a^2}b - {a^3} + \frac{1}{5}{a^2}} \right)\)

\( = 10{a^3}{b^4} - 5{a^4}{b^3} + {a^3}{b^3}\).

b) \(2xy\left( {{x^2} - y} \right) + x\left( {2{y^2} - y} \right) - 2{x^3}y - 1\)

\( = 2{x^3}y - 2x{y^2} + 2x{y^2} - xy - 2{x^3}y - 1\)

\( =  - xy - 1\)

c) \[\left( {{x^3}y + 4{x^2}{y^2} - 5{x^2}{y^3}} \right):xy - x\left( {x - 4{y^2}} \right)\]

\[ = {x^2} + 4xy - 5x{y^2} - {x^2} + 4x{y^2}\]

\[ = 4xy - x{y^2}\]