Thực hiện phép tính: 1) xy {x^2} - 2x{y^2}
Giải thích
1) \(xy\left( {{x^2} - 2x{y^2}} \right) = {x^3}y - 2{x^2}{y^3}.\) 2) \(\left( {x - 2{y^2}} \right)\left( {x + 2{y^2}} \right)\) \( = {\left( x \right)^2} - {\left( {2{y^2}} \right)^2} = {x^2} - 4{y^2}.\) 4) \(\left( {12{x^4}{y^3} - 27{x^3}{y^2} + 5{x^2}{y^2}} \right):\left( { - 3{x^2}{y^2}} \right)\) \( = - 4{x^2}y + 9x - \frac{5}{3}.\) | 3) \(\left( {3x + \frac{1}{2}y} \right)\left( {9{x^2} - \frac{3}{2}xy + \frac{1}{4}{y^2}} \right)\) \( = \left( {3x + \frac{1}{2}y} \right)\left[ {{{\left( {3x} \right)}^2} - 3x.\frac{1}{2}y + {{\left( {\frac{1}{2}y} \right)}^2}} \right]\) \( = {\left( {3x} \right)^3} - {\left( {\frac{1}{2}y} \right)^3}\) \( = 27{x^3} - \frac{{{y^3}}}{8}.\) |