c) (2x + y^2) ^3
f) (2 phần 3x^2 -1 phần 2) ^3
h) ( x – 3y)(x^2 + 3xy +9y^2)
c) (2x + y^2) ^3 f) (2 phần 3x^2 -1 phần 2) ^3 h) ( x – 3y)(x^2 + 3xy +9y^2)
By Madeline
By Madeline
c) (2x + y^2) ^3
f) (2 phần 3x^2 -1 phần 2) ^3
h) ( x – 3y)(x^2 + 3xy +9y^2)
Đáp án + Giải thích các bước giải:
`c)` `(2x+y^2)^3=(2x)^3+3*(2x)^2*y^2+3*2x*(y^2)^2+(y^2)^3` $\\$ `=8x^3+3*4x^2*y^2+3*2x*y^4+y^6=8x^3+12x^2y^2+6xy^4+y^6`
`d)` `(2/3x^2-1/2)^3` $\\$ `=(2/3x^2)^3-3*(2/3x^2)^2*1/2+3*2/3x^2*(1/2)^2-(1/2)^3` $\\$ `= 8/27x^6-3*4/9x^4*1/2+3*2/3x^2*1/4-1/8` $\\$ `=8/27x^6-2/3x^4+1/2x^2-1/8`
`e)` `(x-3y)(x^2+3xy+9y^2)=(x-3y)[x^2+3xy+(3y)^2]=x^3-(3y)^3` $\\$ `=x^3-27y^3`
$c)(2x+y^2)^3$
$=(2x)^3+3×(2x)^2×y^2+3×2x×(y^2)^2+(y^2)^3$
$=8x^3+3×2x^2y^2+3×2xy^4+y^6$
$=8y^3+6x^2y^2+6xy^4+y^6$
`f)(2/3x^2-1/2)^3`
`=(2/3x^2)^3-3×(2/3x^2)^2×1/2+3×2/3x^2×(1/2)^2+(1/2)^3`
`=8/27x^6-3×4/9x^4×1/2+3×2/3x^2×1/4+1/8`
`=8/27x^6-2/3x^4+1/2x^2+1/8`
$h)(x-3y)(x^2-3xy+9y^2)$
$=(x-3y)[x^2-3xy+(3y)^2]$
$=x^3+(3y)^3$
$=x^3+27x^3$
$@ThanhTruc2008$