a) \(\left( {2{x^2} - 3x} \right)\left( {5{x^2} - 2x + 1} \right)\)
b) \(\left( {x - 2y} \right)\left( {3xy + 5{y^2} + x} \right)\) .
Hướng dẫn làm bài:
a) \(\left( {2{x^2} - 3x} \right)\left( {5{x^2} - 2x + 1} \right)\)
=\(2{x^2}.5{x^2} - 2{x^2}.2x + 2{x^2} - 3x.5{x^2} + 3x.2x - 3x\)
=\(10{x^4} - 4{x^3} + 2{x^2} - 15{x^3} + 6{x^2} - 3x\)
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=\(10{x^4} - 19{x^3} + 8{x^2} - 3x\)
b) \(\left( {x - 2y} \right)\left( {3xy + 5{y^2} + x} \right)\)
=\( x.3xy + x.5{y^2} + x.x - 2y.3xy - 2y.5{y^2} - 2y.x\) .
=\(3{x^2}y + 5x{y^2} + {x^2} - 6x{y^2} - 10{y^3} - 2xy\)
=\(3{x^2}y - x{y^2} - 2xy + {x^2} - 10{y^3}\)