Đáp án:
`a, 5x² (3x² -7x +2)`
`= 5x².3x² - 5x².7x + 5x².2`
`= 15x⁴ - 35x³ +10x²`
`b, 2/3 xy (2x² y -3xy +y²)`
`= 2/3 xy. 2x²y - 2/3 xy .3xy +2/3 xy.y²`
`= 4/2 x³ y² - 2x²y² + 2/3 xy³`
`c, (5x-2)(4x-3)`
`= 5x.(4x-3) -2(4x-3)`
`= 20x² -15x -8x +6`
`= 20x² -23x +6`
`d, (2x-3)(5x² -2x+1)`
`= 2x.(5x² -2x+1) -3(5x² -2x+1)`
`= 10x³ -4x² +2x -15x² +6x -3`
`= 10x³ -19x² +8x -3`
`e, (x-2y)(3xy +5y²+x)`
`= x.(3xy+5y²+x) -2y(3xy+5y²+x)`
`= 3x²y +5xy² +x² -6xy² -10y³ -2xy`
`= 3x²y -xy² +x² -10y³ -2xy`
`f, (2x-3)^3`
`= (2x)^3 -3.(2x)^2 .3 + 3.2x.3² -3²`
`= 8x³ -36x³ +54x -27`
`g, (5x -3y)^3`
`= (5x)^3 -3.(5x)^2 .3y + 3.5x.(3y)^2 -(3y)^3`
`= 125x³ -225x²y +135 xy² -27y³`
`h, (2x-3)(4x² +6x+9)`
`= 2x.(4x²+6x +9) -3(4x² +6x +9)`
`= 8x³+12x² +18x -12x² -18x -27`
`= 8x³ -27`