a) 2x * (7x^2 -5x -1)
b) (x^2 + 2xy -3) * (-xy)
c) -2x^3y * (2x^2 – 3 – 3y + 5yz)
d) (3x^n+1 – 2x^n) * 4x^2
Dấu ^ là mũ, dấu * là nhân.
a) 2x * (7x^2 -5x -1) b) (x^2 + 2xy -3) * (-xy) c) -2x^3y * (2x^2 – 3 – 3y + 5yz) d) (3x^n+1 – 2x^n) * 4x^2 Dấu ^ là mũ, dấu * là nhân.
By Clara
`a) 2x(7x^2-5x-1)`
`<=> 14x³-10x²-2x`
`b) (x²+2xy-3)(-xy)`
`<=>-x³y-2x²y²+3xy`
`c) -2x³y(2x²-3-3y+5yz)`
`<=>-4x^5y+6x³y+6x³y²-10x³y²z`
`d) (3x^(n+1)-2x^n)4x²`
`<=>12^(n+3)-8x^(n+2)`
`a) 2x . (7x^2 – 5x – 1)`
` = 2x . 7x^2 – 2x . 5x – 2x . 1`
` = 14x^3 – 10x^2 – 2x`
`b) (x^2 + 2xy – 3) . (-xy)`
` = -xy . x^2 – xy.2xy + 3.xy`
` = -x^3y – 2x^2y^2 + 3xy`
`c) -2x^3y . (2x^2 – 3 – 3y + 5yz)`
` = -2x^3y . 2x^2 + 2x^3y . 3 + 2x^3y . 3y – 2x^3y . 5yz`
` = -4x^5y + 6x^3y + 6x^3y^2 – 10x^3y^2z`
`d) (3x^{n+1} – 2x^n) . 4x^2`
` = 4x^2 . 3x^{n+1} – 4x^2 . 2x^n`
` = 12x^{n+3} – 8x^{n+2}`