Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Ta có
M = ( 2 x + 3 ) ( 4 x 2 – 6 x + 9 ) – 4 ( 2 x 3 – 3 ) = ( 2 x + 3 ) [ ( 2 x ) 2 – 2 x . 3 + 3 2 ] – 8 x 3 + 12 = ( 2 x ) 3 - 3 3 – 8 x 3 + 12 = 8 x 3 + 27 – 8 x 3 + 12 = 39
Vậy giá trị của M là một số lẻ
Đáp án cần chọn là: A
1b.=2((x+y)+(x+y)(x-y)+(x-y))=2(x2-y2+x+y+x-y)=2(x2-y2+2x)=2x2-2y2+4x
2a.=4xy+4xy+2y=8xy+2y=2y(4x+1)
b.=(3x)2+2.3x.y+y2-(2z)2=(3x+y)2-(2z)2=(3x+y-2z)(3x+y+2z)
c.=x2-x-7x+7=x(x-1)-7(x-1)=(x-1)(x-7)
\(\left(x+y\right)^2+2\left(x+y\right)\left(x-y\right)+\left(x-y\right)^2\)
\(=\left(x+y+x-y\right)^2\)
\(=\left(2x\right)^2\)
\(=4x^2\)
hk tốt
^^
1: Ta có: \(\left(x+3\right)\left(x^2-3x+9\right)-\left(x^3+54\right)\)
\(=x^3+27-x^3-54\)
=-27
2: Ta có: \(\left(2x+y\right)\left(4x^2-2xy+y^2\right)-\left(2x-y\right)\left(4x^2+2xy+y^2\right)\)
\(=8x^3+y^3-8x^3+y^3\)
\(=2y^3\)
\(1,=x^3+270-x^3-54=-27\\ 2,=8x^3+y^3-8x^3+y^3=2y^3\\ 3,=x^3-3x^2+3x-1-x^3-8+3x^2-48=3x-57\\ 4,=x^3-x-x^3-1=-x-1\\ 5,=8x^3-5\left(8x^3+1\right)=-32x^3-5\\ 6,=27+x^3-27=x^3\\ 7,làm.ở.câu.3\\ 8,=x^3-6x^2+12x-8+6x^2-12x+6-x^3-1+3x\\ =3x-3\)
a, `(8x^3-4x^2): 4x -(4x^2-5x) : 2x + (2x)^2`
`=4x (2x^2-x) : 4x - 2x(2x-5/2 ) :2x + 4x^2`
`=2x^2-x-2x+5/2+4x^2`
`=6x^2-3x+5/2`
b, `(3x^3-x^2y) :x^2 -(xy^2+x^2y) :xy + 2x(x+1)`
`=x^2 (3x-y) :x^2 -xy(y+x) + (2x^2+2x)`
`=3x-y-y-x+2x^2+2x`
`=2x^2+4x-2y`
a) (x + 3)(x2 – 3x + 9) – (54 + x3)
= ( x + 3)(x2 – 3.x + 32) – (54 + x3)
= x3 + 33 – (54 + x3)
= x3 + 27 – 54 – x3
= -27
b) (2x + y)(4x2 – 2xy + y2) – (2x – y)(4x2 + 2xy + y2)
= (2x + y)[(2x)2 – 2x.y + y2] – (2x – y)[(2x)2 + 2x.y + y2]
= [(2x)3 + y3] – [(2x)3 – y3]
= (2x)3 + y3 – (2x)3 + y3
= 2y3
a) (x + 3)(x2 – 3x + 9) – (54 + x3)
= ( x + 3)(x2 – 3.x + 32) – (54 + x3)
= x3 + 33 – (54 + x3) = x3 + 27 – 54 – x3
= -27
b) (2x + y)(4x2 – 2xy + y2) – (2x – y)(4x2 + 2xy + y2)
= (2x + y)[(2x)2 – 2x.y + y2] – (2x – y)[(2x)2 + 2x.y + y2]
= [(2x)3 + y3] – [(2x)3 – y3]
= (2x)3 + y3 – (2x)3 + y3
= 2y3
Ta có:
8 x 3 - 1 = 2 x 3 - 1 3 = 2 x - 1 . 4 x 2 + 2 x + 1 = - 1 - 2 x . 4 x 2 + 2 x + 1
Do đó, ( 8 x 3 - 1 : 1 - 2 x = - 4 x 2 + 2 x + 1 = - 4 x 2 - 2 x - 1
Chọn B. - 4 x 2 - 2 x - 1
\(=8x^3+27-8x^3-7=20\)
bằng 20