a) 3x( 5x²- 2x - 1 )
= 3x . 5x² + 3x . ( - 2x ) + 3x . ( - 1 )
= 15x³ - 6x² + - 3x
b) ( x² - 2xy + 3 )( - xy )
= - xy . x² - xy . ( - 2xy ) - xy . 3
= - x³y + 2x²y² - 3xy
c) 1/2 x²y ( 2x³ - 2/5xy² - 1 )
= x^5y - 1/5 x³y³ + 1/2x²y
d) 2/7x ( 1,4x - 3,5y )
= 2/5x² - xy
e)1/2xy ( 2/3x² - 3/4xy + 4/5y²
= 1/3x³y - 3/8x²y²+ 2/5xy³
f) ( 1 + 2x - x² ) 5x
= 5x + 10x² - 5x³
g) ( x²y - xy + xy² + y² ) ( 3xy² )
= 3x³y³ - 3 x²y³ + 3x²y^4 + 3xy^4
h) 2/3x²y ( 15x - 0,9y + 6 )
= 15x³y - 3/5 x²y² + 4x²y
i) -3/7 x^4 ( 2,1y² - 0,7x + 35 )
= -9/10 x^4y² - 3/10x^5 -15x^4
j) x ( 2x² + 1 )
= 2x³ +x
k) x² ( 5x³ -x - 1/2 )
= 5x^5 - x³ - 1/2x²
l) 6xy( 2x² + 3y )
= 12x³y + 18xy²
XIN 5s và CẢM Ơn
