Question

Làm tính nhân:

a) x²( 5x³ – x – \(\frac{1}{2}\) )

b) ( 3xy – x² + y ) \(\frac{2}{3}\)x²y;

c) ( 4x³– 5xy + 2x )( \(-\frac{1}{2}\)xy ).

Answer 1

a) x²(5x³ – x - \(\frac{1}{2}\)) = x². 5x³ + x² . (-x) + x² . ( \(-\frac{1}{2}\) )

= 5x⁵ – x³ – \(\frac{1}{2}\)x²

b) (3xy – x² + y) \(\frac{2}{3}\)x²y = \(\frac{2}{3}\)x²y . 3xy + \(\frac{2}{3}\)x²y . (- x²) + \(\frac{2}{3}\)x²y .

y                                    = 2x³y² – \(\frac{2}{3}\)x⁴y + \(\frac{2}{3}\)x²y²

c) (4x³– 5xy + 2x)( \(-\frac{1}{2}\)xy) = \(-\frac{1}{2}\)xy . 4x³ + ( \(-\frac{1}{2}\)xy) . (-5xy) + ( \(-\frac{1}{2}\)xy) . 2x

= -2x⁴y + \(\frac{5}{2}\)x²y² – x²y.