Thực hiện các phép tính :
a, 5x( 2$x^{2}$ – 7x + 8 )
b, -7xy( 3$x^{2}$ – 4x $y^{2}$ + 11 )
c, $\frac{1}{2}$$x^{2}$y ( 2$x^{3}$ – $\frac{2}{5}$x$y^{2}$ – 1 )
d, ( 5x – 2y ).( ( $x^{2}$ – xy + 2 )
e, ( x – 8 ).( x+10 )
Thực hiện các phép tính :
a, 5x( 2$x^{2}$ – 7x + 8 )
b, -7xy( 3$x^{2}$ – 4x $y^{2}$ + 11 )
c, $\frac{1}{2}$$x^{2}$y ( 2$x^{3}$ – $\frac{2}{5}$x$y^{2}$ – 1 )
d, ( 5x – 2y ).( ( $x^{2}$ – xy + 2 )
e, ( x – 8 ).( x+10 )
Đáp án:
Tham khảo
Giải thích các bước giải:
$ a)5x(2x²-7x+8)$
$=10x³-35x²+40x$
$b)-7xy(3x²-4xy²+11)$
$=-21x³y+28x²y³-77xy$
$c)\frac{1}{2}x²y(2x³-\frac{2}{5}xy²-1)$
=$x^5y-\frac{1}{5}x³y³-\frac{1}{2}x²y$
$d)(5x-2y).(x²-xy+2)$
$=5x³-5x²y+10x-2x²y+2xy²-4y$
$=5x³-7x²y+10x+2xy²-4y$
$e)(x-8)(x+10)$
$=x²+10x-8x-80$
$=x²+2x-80$
a)
`5x(2x^2-7x+8)`
`⇔10x^3-35x^2+40x`
b)
`-7xy(3x^2-4xy^2+11)`
`⇔-21x^3y+28x^2y^3-77xy `
c)
`1/2 x^2y(2x^3-2/5xy^2-1)`
`⇔x^5y-1/5x^3y^3-1/2x^2y `
d)
`(5x-2y)(x^2-xy+2)`
`⇔5x^3-5x^2y+10x-2x^2y+2xy^2-4y`
`⇔5x^3-7x^2y+10x-4y `
e)
`(x-8)(x+10)`
`⇔x^2-8x+10x-80`
`⇔x^2+2x-80`