Bài 64 trang 28 SGK Toán 8 tập 1

Làm tính chia:

a) \(( - 2{x^5} + 3{x^2} - 4{x^3}):2{x^2}\);               

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

c) \((3{x^2}{y^2} + 6{x^2}{y^3} - 12xy):3xy\).

a)  \(( - 2{x^5} + 3{x^2} - 4{x^3}):2{x^2} \)

\( =  - \dfrac{2}{2}{x^{(5 - 2)}} + \dfrac{3}{2}{x^{(2 - 2)}} - \dfrac{4}{2}{x^{(3 - 2)}} \)

\(=  - {x^3} + \dfrac{3}{2} - 2x\)

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

\(= \left[ {{x^3}:\left( { - \dfrac{1}{2}x} \right)} \right] + \left[ { - 2{x^2}y:\left( { - \dfrac{1}{2}x} \right)} \right]\)\( + \left[ {3x{y^2}:\left( { - \dfrac{1}{2}x} \right)} \right]\)

\(=  - 2{x^2} + 4xy - 6{y^2}\)

c) \((3{x^2}{y^2} + 6{x^2}{y^3} - 12xy):3xy\) 

\(=(3{x^2}{y^2}:3xy) + (6{x^2}{y^3}:3xy) \)\(+ ( - 12xy:3xy) \)

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